AI Trajectory

Trajectory: (Expand/Collapse All)
Seq	Timestamp	Type	Name	Duration
0/0	2026/09/23 06:44	flow	patch-triage	4m Args: null Results: { "EnableConfigs": [ "XFS_FS", "XFS_RT" ], "FocusSymbols": [ "write_stream_alloc_fd", "write_stream_get_id", "write_stream_pool_init", "write_stream_pool_destroy", "write_stream_release", "xfs_ioc_write_stream_alloc", "xfs_ioc_write_stream_set", "xfs_ioc_write_stream_get_max", "xfs_inode_set_write_stream", "xfs_inode_clear_write_stream", "xfs_inode_max_write_streams", "xfs_buftarg_init_streams", "xfs_bmap_btalloc_write_stream", "xfs_bmap_write_stream_agno", "xfs_bmap_write_stream_rtbno", "fcntl_set_rw_hint" ], "KMSANReasoning": "The patch series introduces generic write stream fd management and integrates write stream awareness into VFS/fcntl, iomap (DIO and writeback), and XFS block allocation.\n\nAn analysis of potential uninitialized memory risks reveals:\n1. Data structures and fields:\n - `struct write_stream` is allocated via `kzalloc_obj` in `write_stream_alloc_fd()`, ensuring all fields are zeroed before assignment.\n - `struct write_stream_pool` bitmap allocations use `bitmap_zalloc`.\n - `inode-\u003ei_write_stream` is explicitly initialized to 0 in `inode_init_always_gfp()`.\n - The newly added field `write_stream` in `struct iomap` is populated in `xfs_bmbt_to_iomap()`, while other iomap consumers benefit from zero-initialization in `iomap_iter_continue()` (via `memset`) and designated initializers (`struct iomap_iter iter = ...`, `struct iomap_writepage_ctx wpc = ...`).\n2. User-space copies / info-leaks:\n - `FS_IOC_WRITE_STREAM_GET_MAX` uses `put_user(max, ...)` where `max` is a fully initialized `__u32` scalar value.\n - `FS_IOC_WRITE_STREAM_ALLOC` returns the file descriptor integer directly.\n - `FS_IOC_WRITE_STREAM_SET` only performs `copy_from_user` to read the input parameters.\n - No structures containing padding or uninitialized fields are copied to user space.\n3. Bug profiles:\n - Potential issues in this patch series pertain to reference counting (`mntget`/`mntput`), synchronization (`i_lock`, `pool-\u003elock`, `XFS_ILOCK`), or lifecycle management/UAF, all of which are properly detected by standard KASAN, LOCKDEP, and UBSAN.\n\nTherefore, there is no uninitialized memory usage or info-leak risk that would require a dedicated KMSAN fuzzing session.", "NeedsKMSAN": false, "Reasoning": "The patch series introduces generic write-stream fd management and integrates write stream allocation and hints into XFS and iomap. It adds new ioctls (FS_IOC_WRITE_STREAM_GET_MAX, FS_IOC_WRITE_STREAM_ALLOC, FS_IOC_WRITE_STREAM_SET), modifies fcntl write hint semantics, introduces anon-inode write-stream fds, and changes AG and realtime block allocation logic in XFS. All changes execute in core VFS/XFS code and are directly reachable from unprivileged/privileged userspace in standard virtualized environments.", "WorthFuzzing": true }
1/1	2026/09/23 06:44	action	read-patch-diff	0m Args: null Results: { "PatchDiff": "commit 86268a1e4affea45948924a7f9d04ec07de91884\nAuthor: syz-cluster \u003ctriage@syzkaller.com\u003e\nDate: Wed Sep 23 06:44:46 2026 +0000\n\n syz-cluster: applied patch under review\n\ndiff --git a/fs/Makefile b/fs/Makefile\nindex 055dfc23d82b6..494da034cef2f 100644\n--- a/fs/Makefile\n+++ b/fs/Makefile\n@@ -23,7 +23,7 @@ obj-$(CONFIG_PROC_FS)\t\t+= proc_namespace.o\n obj-$(CONFIG_LEGACY_DIRECT_IO)\t+= direct-io.o\n obj-y\t\t\t\t+= notify/\n obj-$(CONFIG_EPOLL)\t\t+= eventpoll.o\n-obj-y\t\t\t\t+= anon_inodes.o\n+obj-y\t\t\t\t+= anon_inodes.o write_streams.o\n obj-$(CONFIG_SIGNALFD)\t\t+= signalfd.o\n obj-$(CONFIG_TIMERFD)\t\t+= timerfd.o\n obj-$(CONFIG_EVENTFD)\t\t+= eventfd.o\ndiff --git a/fs/fcntl.c b/fs/fcntl.c\nindex c158f082f1da4..a5439e076197f 100644\n--- a/fs/fcntl.c\n+++ b/fs/fcntl.c\n@@ -380,7 +380,14 @@ static long fcntl_set_rw_hint(struct file file, unsigned long arg)\n \tif (!rw_hint_valid(hint))\n \t\treturn -EINVAL;\n \n+\t/ keep write stream and write life time hint mutually exclusive /\n+\tspin_lock(\u0026inode-\u003ei_lock);\n+\tif (hint != WRITE_LIFE_NOT_SET \u0026\u0026 READ_ONCE(inode-\u003ei_write_stream)) {\n+\t\tspin_unlock(\u0026inode-\u003ei_lock);\n+\t\treturn -EBUSY;\n+\t}\n \tWRITE_ONCE(inode-\u003ei_write_hint, hint);\n+\tspin_unlock(\u0026inode-\u003ei_lock);\n \n \t/\n \t * file-\u003ef_mapping-\u003ehost may differ from inode. As an example,\ndiff --git a/fs/inode.c b/fs/inode.c\nindex ba7da39be4a31..50b91d449a384 100644\n--- a/fs/inode.c\n+++ b/fs/inode.c\n@@ -246,6 +246,7 @@ int inode_init_always_gfp(struct super_block sb, struct inode inode, gfp_t gfp\n \tatomic_set(\u0026inode-\u003ei_writecount, 0);\n \tinode-\u003ei_size = 0;\n \tinode-\u003ei_write_hint = WRITE_LIFE_NOT_SET;\n+\tinode-\u003ei_write_stream = 0;\n \tinode-\u003ei_blocks = 0;\n \tinode-\u003ei_bytes = 0;\n \tinode-\u003ei_generation = 0;\ndiff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c\nindex 8b4039d16ce89..f406a7bc88043 100644\n--- a/fs/iomap/direct-io.c\n+++ b/fs/iomap/direct-io.c\n@@ -349,6 +349,7 @@ static ssize_t iomap_dio_bio_iter_one(struct iomap_iter iter,\n \tfscrypt_set_bio_crypt_ctx(bio, iter-\u003einode, pos, GFP_KERNEL);\n \tbio-\u003ebi_iter.bi_sector = iomap_sector(\u0026iter-\u003eiomap, pos);\n \tbio-\u003ebi_write_hint = iter-\u003einode-\u003ei_write_hint;\n+\tbio-\u003ebi_write_stream = iter-\u003eiomap.write_stream;\n \tbio-\u003ebi_ioprio = dio-\u003eiocb-\u003eki_ioprio;\n \tbio-\u003ebi_private = dio;\n \tbio-\u003ebi_end_io = iomap_dio_bio_end_io;\ndiff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c\nindex 7bbbb417f9152..31a229c12b13d 100644\n--- a/fs/iomap/ioend.c\n+++ b/fs/iomap/ioend.c\n@@ -166,6 +166,7 @@ static struct iomap_ioend iomap_alloc_ioend(struct iomap_writepage_ctx wpc,\n \t\t\t GFP_NOFS, \u0026iomap_ioend_bioset);\n \tbio-\u003ebi_iter.bi_sector = iomap_sector(\u0026wpc-\u003eiomap, pos);\n \tbio-\u003ebi_write_hint = wpc-\u003einode-\u003ei_write_hint;\n+\tbio-\u003ebi_write_stream = wpc-\u003eiomap.write_stream;\n \twbc_init_bio(wpc-\u003ewbc, bio);\n \twpc-\u003enr_folios = 0;\n \treturn iomap_init_ioend(wpc-\u003einode, bio, pos, ioend_flags);\n@@ -189,6 +190,8 @@ static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx wpc, loff_t pos,\n \tif (!(wpc-\u003eiomap.flags \u0026 IOMAP_F_ANON_WRITE) \u0026\u0026\n \t iomap_sector(\u0026wpc-\u003eiomap, pos) != bio_end_sector(\u0026ioend-\u003eio_bio))\n \t\treturn false;\n+\tif (wpc-\u003eiomap.write_stream != ioend-\u003eio_bio.bi_write_stream)\n+\t\treturn false;\n \t/\n \t Limit ioend bio chain lengths to minimise IO completion latency. This\n \t * also prevents long tight loops ending page writeback on all the\ndiff --git a/fs/write_streams.c b/fs/write_streams.c\nnew file mode 100644\nindex 0000000000000..b7f6ca6cf7250\n--- /dev/null\n+++ b/fs/write_streams.c\n@@ -0,0 +1,138 @@\n+// SPDX-License-Identifier: GPL-2.0\n+/* Generic write-stream fd management. /\n+#include \u003clinux/anon_inodes.h\u003e\n+#include \u003clinux/bitmap.h\u003e\n+#include \u003clinux/err.h\u003e\n+#include \u003clinux/file.h\u003e\n+#include \u003clinux/fs.h\u003e\n+#include \u003clinux/mount.h\u003e\n+#include \u003clinux/slab.h\u003e\n+#include \u003clinux/write_streams.h\u003e\n+\n+struct write_stream {\n+\tstruct write_stream_pool\tpool;\n+\tstruct vfsmount\t\t\tmnt;\t/ pins the mount /\n+\tu16\t\t\t\tid;\t/ 1-based slot number /\n+};\n+\n+static int write_stream_release(struct inode inode, struct file file)\n+{\n+\tstruct write_stream ws = file-\u003eprivate_data;\n+\n+\tspin_lock(\u0026ws-\u003epool-\u003elock);\n+\t__clear_bit(ws-\u003eid - 1, ws-\u003epool-\u003estreams_in_use);\n+\tspin_unlock(\u0026ws-\u003epool-\u003elock);\n+\tmntput(ws-\u003emnt);\n+\tkfree(ws);\n+\treturn 0;\n+}\n+\n+static const struct file_operations write_stream_fops = {\n+\t.release\t= write_stream_release,\n+\t.llseek\t\t= noop_llseek,\n+};\n+\n+/*\n+ write_stream_pool_init - size a write stream pool\n+ * @pool: pool to initialise\n+ * @nr: number of slots, may be zero\n+ \n+ Returns 0, or -ENOMEM if the bitmap cannot be allocated.\n+ /\n+int write_stream_pool_init(struct write_stream_pool pool, unsigned int nr)\n+{\n+\tspin_lock_init(\u0026pool-\u003elock);\n+\tpool-\u003estreams_in_use = NULL;\n+\tpool-\u003enr_streams = 0;\n+\n+\tif (!nr)\n+\t\treturn 0;\n+\n+\tpool-\u003estreams_in_use = bitmap_zalloc(nr, GFP_KERNEL);\n+\tif (!pool-\u003estreams_in_use)\n+\t\treturn -ENOMEM;\n+\tpool-\u003enr_streams = nr;\n+\treturn 0;\n+}\n+EXPORT_SYMBOL_GPL(write_stream_pool_init);\n+\n+/*\n+ write_stream_pool_destroy - free a write stream pool\n+ * @pool: pool to release\n+ /\n+void write_stream_pool_destroy(struct write_stream_pool pool)\n+{\n+\tbitmap_free(pool-\u003estreams_in_use);\n+\tpool-\u003estreams_in_use = NULL;\n+\tpool-\u003enr_streams = 0;\n+}\n+EXPORT_SYMBOL_GPL(write_stream_pool_destroy);\n+\n+/*\n+ write_stream_alloc_fd - reserve a slot and return an fd naming it\n+ * @pool: pool to reserve from\n+ * @file: file whose mount is pinned for the life of the stream\n+ \n+ Returns an O_RDONLY \| O_CLOEXEC fd, -EOPNOTSUPP if the pool has no slots,\n+ * or -EBUSY if they are all taken.\n+ /\n+int write_stream_alloc_fd(struct write_stream_pool pool, struct file file)\n+{\n+\tstruct write_stream ws;\n+\tunsigned int slot;\n+\tint fd;\n+\n+\tif (!pool-\u003enr_streams)\n+\t\treturn -EOPNOTSUPP;\n+\n+\tws = kzalloc_obj(ws, GFP_KERNEL);\n+\tif (!ws)\n+\t\treturn -ENOMEM;\n+\n+\tspin_lock(\u0026pool-\u003elock);\n+\tslot = find_first_zero_bit(pool-\u003estreams_in_use, pool-\u003enr_streams);\n+\tif (slot \u003e= pool-\u003enr_streams) {\n+\t\tspin_unlock(\u0026pool-\u003elock);\n+\t\tkfree(ws);\n+\t\treturn -EBUSY;\n+\t}\n+\t__set_bit(slot, pool-\u003estreams_in_use);\n+\tspin_unlock(\u0026pool-\u003elock);\n+\n+\tws-\u003epool = pool;\n+\tws-\u003emnt = mntget(file-\u003ef_path.mnt);\n+\tws-\u003eid = slot + 1;\n+\n+\tfd = anon_inode_getfd(\"[write_stream]\", \u0026write_stream_fops, ws,\n+\t\t\t O_RDONLY \| O_CLOEXEC);\n+\tif (fd \u003c 0) {\n+\t\tspin_lock(\u0026pool-\u003elock);\n+\t\t__clear_bit(slot, pool-\u003estreams_in_use);\n+\t\tspin_unlock(\u0026pool-\u003elock);\n+\t\tmntput(ws-\u003emnt);\n+\t\tkfree(ws);\n+\t}\n+\treturn fd;\n+}\n+EXPORT_SYMBOL_GPL(write_stream_alloc_fd);\n+\n+/\n+ write_stream_get_id - the id a stream file names\n+ * @file: candidate stream file\n+ * @pool: pool the stream must belong to, or NULL to accept any\n+ \n+ Returns the 1-based id, or -EINVAL if @file is not a stream file, or is\n+ * a stream of a different pool.\n+ /\n+int write_stream_get_id(struct file file, const struct write_stream_pool pool)\n+{\n+\tstruct write_stream ws;\n+\n+\tif (file-\u003ef_op != \u0026write_stream_fops)\n+\t\treturn -EINVAL;\n+\tws = file-\u003eprivate_data;\n+\tif (pool \u0026\u0026 ws-\u003epool != pool)\n+\t\treturn -EINVAL;\n+\treturn ws-\u003eid;\n+}\n+EXPORT_SYMBOL_GPL(write_stream_get_id);\ndiff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c\nindex d64defeda645e..2e83811cefcbc 100644\n--- a/fs/xfs/libxfs/xfs_bmap.c\n+++ b/fs/xfs/libxfs/xfs_bmap.c\n@@ -3579,8 +3579,31 @@ xfs_bmap_btalloc_filestreams(\n \treturn xfs_bmap_btalloc_low_space(ap, args);\n }\n \n+static xfs_agnumber_t\n+xfs_bmap_write_stream_agno(\n+\tstruct xfs_inode\tip,\n+\tunsigned int\t\tstream_id)\n+{\n+\tstruct xfs_mount\tmp = ip-\u003ei_mount;\n+\txfs_agnumber_t\t\tnr_ags = mp-\u003em_sb.sb_agcount;\n+\tunsigned int\t\tnr_streams =\n+\t\twrite_stream_pool_count(\u0026mp-\u003em_ddev_targp-\u003ebt_stream_pool);\n+\txfs_agnumber_t\t\tag_set_size, start_agno;\n+\n+\tstream_id -= 1;\t/* convert from 1-based to 0-based /\n+\tag_set_size = nr_ags / nr_streams;\n+\tstart_agno = stream_id ag_set_size;\n+\n+\t/* last stream absorbs any uneven remainder /\n+\tif (stream_id == nr_streams - 1)\n+\t\tag_set_size = nr_ags - start_agno;\n+\n+\treturn start_agno + I_INO(ip) % ag_set_size;\n+}\n+\n+/ Core AG allocator. The caller sets ap-\u003eblkno to the target AG start. /\n static int\n-xfs_bmap_btalloc_best_length(\n+xfs_bmap_btalloc_from_blkno(\n \tstruct xfs_bmalloca\tap,\n \tstruct xfs_alloc_arg\targs,\n \tint\t\t\tstripe_align)\n@@ -3588,7 +3611,6 @@ xfs_bmap_btalloc_best_length(\n \txfs_extlen_t\t\tblen = 0;\n \tint\t\t\terror;\n \n-\tap-\u003eblkno = XFS_INODE_TO_FSB(ap-\u003eip);\n \tif (!xfs_bmap_adjacent(ap))\n \t\tap-\u003eeof = false;\n \n@@ -3621,6 +3643,32 @@ xfs_bmap_btalloc_best_length(\n \treturn xfs_bmap_btalloc_low_space(ap, args);\n }\n \n+/ Start a write-stream file in the AG set that backs its stream. /\n+static int\n+xfs_bmap_btalloc_write_stream(\n+\tstruct xfs_bmalloca\tap,\n+\tstruct xfs_alloc_arg\targs,\n+\tint\t\t\tstripe_align,\n+\tunsigned int\t\tstream_id)\n+{\n+\tstruct xfs_mount\tmp = ap-\u003eip-\u003ei_mount;\n+\txfs_agnumber_t\t\tagno;\n+\n+\tagno = xfs_bmap_write_stream_agno(ap-\u003eip, stream_id);\n+\tap-\u003eblkno = XFS_AGB_TO_FSB(mp, agno, 0);\n+\treturn xfs_bmap_btalloc_from_blkno(ap, args, stripe_align);\n+}\n+\n+static int\n+xfs_bmap_btalloc_best_length(\n+\tstruct xfs_bmalloca\tap,\n+\tstruct xfs_alloc_arg\targs,\n+\tint\t\t\tstripe_align)\n+{\n+\tap-\u003eblkno = XFS_INODE_TO_FSB(ap-\u003eip);\n+\treturn xfs_bmap_btalloc_from_blkno(ap, args, stripe_align);\n+}\n+\n static int\n xfs_bmap_btalloc(\n \tstruct xfs_bmalloca\tap)\n@@ -3640,6 +3688,7 @@ xfs_bmap_btalloc(\n \t};\n \txfs_fileoff_t\t\torig_offset;\n \txfs_extlen_t\t\torig_length;\n+\tunsigned int\t\tstream_id;\n \tint\t\t\terror;\n \tint\t\t\tstripe_align;\n \n@@ -3652,11 +3701,16 @@ xfs_bmap_btalloc(\n \t/ Trim the allocation back to the maximum an AG can fit. /\n \targs.maxlen = min(ap-\u003elength, mp-\u003em_ag_max_usable);\n \n+\tstream_id = READ_ONCE(VFS_I(ap-\u003eip)-\u003ei_write_stream);\n+\n \tif (unlikely(XFS_TEST_ERROR(mp, XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT)))\n \t\terror = xfs_bmap_exact_minlen_extent_alloc(ap, \u0026args);\n \telse if ((ap-\u003edatatype \u0026 XFS_ALLOC_USERDATA) \u0026\u0026\n \t\t\txfs_inode_is_filestream(ap-\u003eip))\n \t\terror = xfs_bmap_btalloc_filestreams(ap, \u0026args, stripe_align);\n+\telse if ((ap-\u003edatatype \u0026 XFS_ALLOC_USERDATA) \u0026\u0026 stream_id)\n+\t\terror = xfs_bmap_btalloc_write_stream(ap, \u0026args, stripe_align,\n+\t\t\t\tstream_id);\n \telse\n \t\terror = xfs_bmap_btalloc_best_length(ap, \u0026args, stripe_align);\n \tif (error)\ndiff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c\nindex 8256c1d13ce20..1748be9aa7d65 100644\n--- a/fs/xfs/xfs_buf.c\n+++ b/fs/xfs/xfs_buf.c\n@@ -1647,6 +1647,7 @@ void\n xfs_free_buftarg(\n \tstruct xfs_buftarg\tbtp)\n {\n+\twrite_stream_pool_destroy(\u0026btp-\u003ebt_stream_pool);\n \txfs_destroy_buftarg(btp);\n \tfs_put_dax(btp-\u003ebt_daxdev, btp-\u003ebt_mount);\n \t/* the main block device is closed by kill_block_super /\n@@ -1684,6 +1685,40 @@ xfs_configure_buftarg_atomic_writes(\n \tbtp-\u003ebt_awu_max = max_bytes;\n }\n \n+#define XFS_MAX_SW_WRITE_STREAMS\tU8_MAX\n+\n+/ Heuristic to derive software write stream count from a group topology /\n+static unsigned int\n+xfs_sw_write_stream_count(\n+\tunsigned int\t\tnr_groups)\n+{\n+\tunsigned int\t\tgroup_set_size;\n+\n+\tif (nr_groups \u003e= 16)\n+\t\tgroup_set_size = 4;\n+\telse if (nr_groups \u003e= 8)\n+\t\tgroup_set_size = 2;\n+\telse\n+\t\tgroup_set_size = 1;\n+\treturn min(nr_groups / group_set_size, XFS_MAX_SW_WRITE_STREAMS);\n+}\n+\n+int\n+xfs_buftarg_init_streams(\n+\tstruct xfs_buftarg\tbtp,\n+\tunsigned int\t\tnr_groups)\n+{\n+\tunsigned int\t\tnr_streams;\n+\tunsigned int\t\thw_streams;\n+\n+\thw_streams = bdev_max_write_streams(btp-\u003ebt_bdev);\n+\tif (hw_streams)\n+\t\tnr_streams = min(hw_streams, nr_groups);\n+\telse\n+\t\tnr_streams = xfs_sw_write_stream_count(nr_groups);\n+\treturn write_stream_pool_init(\u0026btp-\u003ebt_stream_pool, nr_streams);\n+}\n+\n /* Configure a buffer target that abstracts a block device. /\n int\n xfs_configure_buftarg(\ndiff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h\nindex a4729253b56fd..b5292e5731e38 100644\n--- a/fs/xfs/xfs_buf.h\n+++ b/fs/xfs/xfs_buf.h\n@@ -15,6 +15,7 @@\n #include \u003clinux/uio.h\u003e\n #include \u003clinux/list_lru.h\u003e\n #include \u003clinux/lockref.h\u003e\n+#include \u003clinux/write_streams.h\u003e\n \n extern struct kmem_cache xfs_buf_cache;\n \n@@ -102,6 +103,9 @@ struct xfs_buftarg {\n \tunsigned int\t\tbt_awu_min;\n \tunsigned int\t\tbt_awu_max;\n \n+\t/* slot pool for stream fds on this device /\n+\tstruct write_stream_pool bt_stream_pool;\n+\n \tstruct rhashtable\tbt_hash;\n };\n \n@@ -360,6 +364,8 @@ extern void xfs_buftarg_wait(struct xfs_buftarg );\n extern void xfs_buftarg_drain(struct xfs_buftarg );\n int xfs_configure_buftarg(struct xfs_buftarg btp, unsigned int sectorsize,\n \t\txfs_fsblock_t nr_blocks);\n+int xfs_buftarg_init_streams(struct xfs_buftarg btp,\n+\t\tunsigned int nr_groups);\n \n #define xfs_readonly_buftarg(buftarg)\tbdev_read_only((buftarg)-\u003ebt_bdev)\n \ndiff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c\nindex 030a7c8f2c129..c3503fe870bad 100644\n--- a/fs/xfs/xfs_inode.c\n+++ b/fs/xfs/xfs_inode.c\n@@ -4,6 +4,7 @@\n All Rights Reserved.\n /\n #include \u003clinux/iversion.h\u003e\n+#include \u003clinux/write_streams.h\u003e\n \n #include \"xfs_platform.h\"\n #include \"xfs_fs.h\"\n@@ -47,6 +48,74 @@\n \n struct kmem_cache xfs_inode_cache;\n \n+/* Number of write streams available to this inode. /\n+int\n+xfs_inode_max_write_streams(\n+\tstruct xfs_inode\tip)\n+{\n+\txfs_assert_ilocked(ip, XFS_ILOCK_SHARED \| XFS_ILOCK_EXCL);\n+\n+\tif (xfs_inode_is_filestream(ip))\n+\t\treturn 0;\n+\tif (XFS_IS_REALTIME_INODE(ip) \u0026\u0026 xfs_has_zoned(ip-\u003ei_mount))\n+\t\treturn 0;\n+\treturn write_stream_pool_count(\u0026xfs_inode_buftarg(ip)-\u003ebt_stream_pool);\n+}\n+\n+/* Bind the write stream named by @stream_fd to @ip /\n+int\n+xfs_inode_set_write_stream(\n+\tstruct xfs_inode\tip,\n+\tint\t\t\tstream_fd)\n+{\n+\tCLASS(fd, f)(stream_fd);\n+\tstruct xfs_buftarg\ttarget;\n+\tint\t\t\tid, error = 0;\n+\n+\tif (!fd_file(f))\n+\t\treturn -EBADF;\n+\txfs_ilock(ip, XFS_ILOCK_EXCL);\n+\tif (XFS_IS_REALTIME_INODE(ip) \u0026\u0026 xfs_has_zoned(ip-\u003ei_mount)) {\n+\t\terror = -EINVAL;\n+\t\tgoto out_unlock;\n+\t}\n+\n+\ttarget = xfs_inode_buftarg(ip);\n+\tid = write_stream_get_id(fd_file(f), \u0026target-\u003ebt_stream_pool);\n+\tif (id \u003c 0) {\n+\t\terror = id;\n+\t\tgoto out_unlock;\n+\t}\n+\n+\t/ Filestream and write-stream are mutually exclusive /\n+\tif (xfs_inode_is_filestream(ip)) {\n+\t\terror = -EINVAL;\n+\t\tgoto out_unlock;\n+\t}\n+\n+\t/ keep write stream and write life time hint mutually exclusive /\n+\tspin_lock(\u0026VFS_I(ip)-\u003ei_lock);\n+\tif (VFS_I(ip)-\u003ei_write_hint != WRITE_LIFE_NOT_SET) {\n+\t\tspin_unlock(\u0026VFS_I(ip)-\u003ei_lock);\n+\t\terror = -EBUSY;\n+\t\tgoto out_unlock;\n+\t}\n+\tWRITE_ONCE(VFS_I(ip)-\u003ei_write_stream, id);\n+\tspin_unlock(\u0026VFS_I(ip)-\u003ei_lock);\n+out_unlock:\n+\txfs_iunlock(ip, XFS_ILOCK_EXCL);\n+\treturn error;\n+}\n+\n+void\n+xfs_inode_clear_write_stream(\n+\tstruct xfs_inode\tip)\n+{\n+\txfs_ilock(ip, XFS_ILOCK_EXCL);\n+\tWRITE_ONCE(VFS_I(ip)-\u003ei_write_stream, 0);\n+\txfs_iunlock(ip, XFS_ILOCK_EXCL);\n+}\n+\n /\n These two are wrapper routines around the xfs_ilock() routine used to\n * centralize some grungy code. They are used in places that wish to lock the\ndiff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h\nindex 1602027cd0aa5..c053f105d2fa8 100644\n--- a/fs/xfs/xfs_inode.h\n+++ b/fs/xfs/xfs_inode.h\n@@ -672,4 +672,8 @@ int xfs_icreate_dqalloc(const struct xfs_icreate_args args,\n \t\tstruct xfs_dquot udqpp, struct xfs_dquot gdqpp,\n \t\tstruct xfs_dquot pdqpp);\n \n+int xfs_inode_max_write_streams(struct xfs_inode ip);\n+int xfs_inode_set_write_stream(struct xfs_inode ip, int stream_fd);\n+void xfs_inode_clear_write_stream(struct xfs_inode ip);\n+\n #endif\t/* __XFS_INODE_H__ /\ndiff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c\nindex 96ca3e480cb9f..4c0aff34e3c3d 100644\n--- a/fs/xfs/xfs_ioctl.c\n+++ b/fs/xfs/xfs_ioctl.c\n@@ -557,6 +557,12 @@ xfs_ioctl_setattr_xflags(\n \tbool\t\t\trtflag = (fa-\u003efsx_xflags \u0026 FS_XFLAG_REALTIME);\n \tuint64_t\t\ti_flags2;\n \n+\t/ refuse a filestream/realtime flag change while a stream is attached /\n+\tif (READ_ONCE(VFS_I(ip)-\u003ei_write_stream) \u0026\u0026\n+\t ((fa-\u003efsx_xflags \u0026 FS_XFLAG_FILESTREAM) \|\|\n+\t rtflag != XFS_IS_REALTIME_INODE(ip)))\n+\t\treturn -EINVAL;\n+\n \tif (rtflag != XFS_IS_REALTIME_INODE(ip)) {\n \t\t/ Can't change realtime flag if any extents are allocated. /\n \t\tif (xfs_inode_has_filedata(ip))\n@@ -1200,6 +1206,73 @@ xfs_ioctl_fs_counts(\n \treturn 0;\n }\n \n+static int\n+xfs_ioc_write_stream_get_max(\n+\tstruct file\t\tfilp,\n+\tvoid __user\t\targ)\n+{\n+\tstruct xfs_inode\tip = XFS_I(file_inode(filp));\n+\t__u32\t\t\tmax;\n+\n+\txfs_ilock(ip, XFS_ILOCK_SHARED);\n+\tmax = xfs_inode_max_write_streams(ip);\n+\txfs_iunlock(ip, XFS_ILOCK_SHARED);\n+\n+\treturn put_user(max, (__u32 __user )arg);\n+}\n+\n+static int\n+xfs_ioc_write_stream_alloc(\n+\tstruct file\t\tfilp)\n+{\n+\tstruct xfs_inode\tip = XFS_I(file_inode(filp));\n+\tstruct xfs_buftarg\ttarget;\n+\tint\t\t\tmax;\n+\n+\tif (!capable(CAP_SYS_ADMIN))\n+\t\treturn -EPERM;\n+\n+\txfs_ilock(ip, XFS_ILOCK_SHARED);\n+\tmax = xfs_inode_max_write_streams(ip);\n+\ttarget = xfs_inode_buftarg(ip);\n+\txfs_iunlock(ip, XFS_ILOCK_SHARED);\n+\n+\tif (!max)\n+\t\treturn -EOPNOTSUPP;\n+\treturn write_stream_alloc_fd(\u0026target-\u003ebt_stream_pool, filp);\n+}\n+\n+static int\n+xfs_ioc_write_stream_set(\n+\tstruct file\t\tfilp,\n+\tvoid __user\t\targ)\n+{\n+\tstruct xfs_inode\tip = XFS_I(file_inode(filp));\n+\tstruct fs_write_stream_set set;\n+\n+\tif (!(filp-\u003ef_mode \u0026 FMODE_WRITE))\n+\t\treturn -EBADF;\n+\tif (copy_from_user(\u0026set, arg, sizeof(set)))\n+\t\treturn -EFAULT;\n+\tif (set.flags \u0026 ~FS_WRITE_STREAM_SET_CLEAR)\n+\t\treturn -EINVAL;\n+\n+\t/ Regular files only. /\n+\tif (!S_ISREG(VFS_I(ip)-\u003ei_mode))\n+\t\treturn -EINVAL;\n+\n+\tif (!inode_owner_or_capable(file_mnt_idmap(filp), VFS_I(ip)))\n+\t\treturn -EPERM;\n+\n+\tif (set.flags \u0026 FS_WRITE_STREAM_SET_CLEAR) {\n+\t\tif (set.stream_fd != -1)\n+\t\t\treturn -EINVAL;\n+\t\txfs_inode_clear_write_stream(ip);\n+\t\treturn 0;\n+\t}\n+\treturn xfs_inode_set_write_stream(ip, set.stream_fd);\n+}\n+\n /\n * These long-unused ioctls were removed from the official ioctl API in 5.17,\n * but retain these definitions so that we can log warnings about them.\n@@ -1466,6 +1539,13 @@ xfs_file_ioctl(\n \tcase XFS_IOC_VERIFY_MEDIA:\n \t\treturn xfs_ioc_verify_media(filp, arg);\n \n+\tcase FS_IOC_WRITE_STREAM_GET_MAX:\n+\t\treturn xfs_ioc_write_stream_get_max(filp, arg);\n+\tcase FS_IOC_WRITE_STREAM_ALLOC:\n+\t\treturn xfs_ioc_write_stream_alloc(filp);\n+\tcase FS_IOC_WRITE_STREAM_SET:\n+\t\treturn xfs_ioc_write_stream_set(filp, (void __user )arg);\n+\n \tdefault:\n \t\treturn -ENOTTY;\n \t}\ndiff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c\nindex 7c6238fed61e4..3e9df790a544e 100644\n--- a/fs/xfs/xfs_iomap.c\n+++ b/fs/xfs/xfs_iomap.c\n@@ -144,6 +144,7 @@ xfs_bmbt_to_iomap(\n \t}\n \tiomap-\u003eoffset = XFS_FSB_TO_B(mp, imap-\u003ebr_startoff);\n \tiomap-\u003elength = XFS_FSB_TO_B(mp, imap-\u003ebr_blockcount);\n+\tiomap-\u003ewrite_stream = READ_ONCE(VFS_I(ip)-\u003ei_write_stream);\n \tif (mapping_flags \u0026 IOMAP_DAX) {\n \t\tiomap-\u003edax_dev = target-\u003ebt_daxdev;\n \t} else {\ndiff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c\nindex 84efe5a8fb11d..a291f1aca6eb4 100644\n--- a/fs/xfs/xfs_rtalloc.c\n+++ b/fs/xfs/xfs_rtalloc.c\n@@ -2160,6 +2160,28 @@ xfs_rtallocate_align(\n \treturn 0;\n }\n \n+static xfs_rtblock_t\n+xfs_bmap_write_stream_rtbno(\n+\tstruct xfs_inode\tip,\n+\tunsigned int\t\tstream_id)\n+{\n+\tstruct xfs_mount\tmp = ip-\u003ei_mount;\n+\tunsigned int\t\tnr_rtgs = mp-\u003em_sb.sb_rgcount;\n+\tunsigned int\t\tnr_streams =\n+\t\twrite_stream_pool_count(\u0026mp-\u003em_rtdev_targp-\u003ebt_stream_pool);\n+\tunsigned int\t\tset_size = nr_rtgs / nr_streams;\n+\txfs_rgnumber_t\t\tstart_rgno, target_rgno;\n+\n+\tstream_id -= 1;\t/ convert from 1-based to 0-based /\n+\tstart_rgno = stream_id set_size;\n+\tif (stream_id == nr_streams - 1)\n+\t\tset_size = nr_rtgs - start_rgno;\n+\ttarget_rgno = start_rgno + I_INO(ip) % set_size;\n+\n+\treturn (xfs_rtblock_t)target_rgno \u003c\u003c\n+\t\tmp-\u003em_groups[XG_TYPE_RTG].blklog;\n+}\n+\n int\n xfs_bmap_rtalloc(\n \tstruct xfs_bmalloca\tap)\n@@ -2174,10 +2196,13 @@ xfs_bmap_rtalloc(\n \tbool\t\t\tnoalign = false;\n \tbool\t\t\tinitial_user_data =\n \t\tap-\u003edatatype \u0026 XFS_ALLOC_INITIAL_USER_DATA;\n+\tunsigned int\t\tstream_id;\n \tint\t\t\terror;\n \n \tASSERT(!xfs_has_zoned(ap-\u003etp-\u003et_mountp));\n \n+\tstream_id = READ_ONCE(VFS_I(ap-\u003eip)-\u003ei_write_stream);\n+\n retry:\n \terror = xfs_rtallocate_align(ap, \u0026ralen, \u0026raminlen, \u0026prod, \u0026noalign);\n \tif (error)\n@@ -2185,6 +2210,8 @@ xfs_bmap_rtalloc(\n \n \tif (xfs_bmap_adjacent(ap))\n \t\tbno_hint = ap-\u003eblkno;\n+\telse if (stream_id \u0026\u0026 xfs_has_rtgroups(ap-\u003eip-\u003ei_mount))\n+\t\tbno_hint = xfs_bmap_write_stream_rtbno(ap-\u003eip, stream_id);\n \n \tif (xfs_has_rtgroups(ap-\u003eip-\u003ei_mount)) {\n \t\terror = xfs_rtallocate_rtgs(ap-\u003etp, bno_hint, raminlen, ralen,\ndiff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c\nindex b24db75eaedc5..5c92f8ebd8a73 100644\n--- a/fs/xfs/xfs_super.c\n+++ b/fs/xfs/xfs_super.c\n@@ -608,6 +608,11 @@ xfs_setup_devices(\n \tif (error)\n \t\treturn error;\n \n+\terror = xfs_buftarg_init_streams(mp-\u003em_ddev_targp,\n+\t\t\tmp-\u003em_sb.sb_agcount);\n+\tif (error)\n+\t\treturn error;\n+\n \tif (mp-\u003em_logdev_targp \u0026\u0026 mp-\u003em_logdev_targp != mp-\u003em_ddev_targp) {\n \t\tunsigned int\tlog_sector_size = BBSIZE;\n \n@@ -632,6 +637,13 @@ xfs_setup_devices(\n \t\tif (error)\n \t\t\treturn error;\n \t\txfs_update_bdi_rahead(mp);\n+\n+\t\tif (xfs_has_rtgroups(mp) \u0026\u0026 !xfs_has_zoned(mp)) {\n+\t\t\terror = xfs_buftarg_init_streams(mp-\u003em_rtdev_targp,\n+\t\t\t\t\tmp-\u003em_sb.sb_rgcount);\n+\t\t\tif (error)\n+\t\t\t\treturn error;\n+\t\t}\n \t}\n \n \treturn 0;\ndiff --git a/include/linux/fs.h b/include/linux/fs.h\nindex f9d1e05e8ae68..3d9ce4d30cd54 100644\n--- a/include/linux/fs.h\n+++ b/include/linux/fs.h\n@@ -812,7 +812,7 @@ struct inode {\n \n \t/ Misc /\n \tstruct inode_state_flags i_state;\n-\t/ 32-bit hole /\n+\tu16\t\t\ti_write_stream;\n \tstruct rw_semaphore\ti_rwsem;\n \n \tunsigned long\t\tdirtied_when;\t/ jiffies of first dirtying /\ndiff --git a/include/linux/iomap.h b/include/linux/iomap.h\nindex bc7ae6327dbf8..f923778f08bd7 100644\n--- a/include/linux/iomap.h\n+++ b/include/linux/iomap.h\n@@ -133,6 +133,7 @@ struct iomap {\n \tu64\t\t\tlength;\t/ length of mapping, bytes /\n \tu16\t\t\ttype;\t/ type of mapping /\n \tu16\t\t\tflags;\t/ flags for mapping /\n+\tu16\t\t\twrite_stream; / write stream for I/O /\n \tstruct block_device\tbdev;\t/* block device for I/O /\n \tstruct dax_device\tdax_dev; /* dax_dev for dax operations /\n \tvoid\t\t\tinline_data;\ndiff --git a/include/linux/write_streams.h b/include/linux/write_streams.h\nnew file mode 100644\nindex 0000000000000..d27f42df59845\n--- /dev/null\n+++ b/include/linux/write_streams.h\n@@ -0,0 +1,33 @@\n+/* SPDX-License-Identifier: GPL-2.0 /\n+#ifndef _LINUX_WRITE_STREAMS_H\n+#define _LINUX_WRITE_STREAMS_H\n+\n+#include \u003clinux/spinlock.h\u003e\n+#include \u003clinux/types.h\u003e\n+\n+struct file;\n+\n+/\n+ * Write stream slot pool, embedded in whatever filesystem object scopes\n+ * an id space.\n+ /\n+struct write_stream_pool {\n+\tunsigned int\t\tnr_streams;\n+\tunsigned long\t\tstreams_in_use;\n+\tspinlock_t\t\tlock;\n+};\n+\n+static inline unsigned int\n+write_stream_pool_count(const struct write_stream_pool pool)\n+{\n+\treturn pool-\u003enr_streams;\n+}\n+\n+int write_stream_pool_init(struct write_stream_pool pool, unsigned int nr);\n+void write_stream_pool_destroy(struct write_stream_pool pool);\n+\n+int write_stream_alloc_fd(struct write_stream_pool pool, struct file file);\n+int write_stream_get_id(struct file file,\n+\t\t\t const struct write_stream_pool pool);\n+\n+#endif / _LINUX_WRITE_STREAMS_H /\ndiff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h\nindex 34c6f219462a5..1974052aa476b 100644\n--- a/include/uapi/linux/fs.h\n+++ b/include/uapi/linux/fs.h\n@@ -345,6 +345,21 @@ struct file_attr {\n / Get logical block metadata capability details /\n #define FS_IOC_GETLBMD_CAP\t\t_IOWR(0x15, 2, struct logical_block_metadata_cap)\n \n+struct fs_write_stream_set {\n+\t__s32\t\tstream_fd;\t/ IN: stream to attach, -1 to clear /\n+\t__u32\t\tflags;\t\t/ IN: FS_WRITE_STREAM_SET_* /\n+};\n+\n+/ Clear the file's write stream. Requires stream_fd to be -1. /\n+#define FS_WRITE_STREAM_SET_CLEAR\t(1U \u003c\u003c 0)\n+\n+/ GET_MAX returns the count through its argument; ALLOC returns a stream fd\n+ * as the ioctl return value and takes none.\n+ /\n+#define FS_IOC_WRITE_STREAM_GET_MAX\t_IOR(0x15, 3, __u32)\n+#define FS_IOC_WRITE_STREAM_ALLOC\t_IO(0x15, 4)\n+#define FS_IOC_WRITE_STREAM_SET\t\t_IOW(0x15, 5, struct fs_write_stream_set)\n+\n /\n * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS)\n *\n" }
2/1	2026/09/23 06:44	agent	patch-evaluator	1m Model: core Args: null Results: { "EnableConfigs": [ "XFS_FS", "XFS_RT" ], "FocusSymbols": [ "write_stream_alloc_fd", "write_stream_get_id", "write_stream_pool_init", "write_stream_pool_destroy", "write_stream_release", "xfs_ioc_write_stream_alloc", "xfs_ioc_write_stream_set", "xfs_ioc_write_stream_get_max", "xfs_inode_set_write_stream", "xfs_inode_clear_write_stream", "xfs_inode_max_write_streams", "xfs_buftarg_init_streams", "xfs_bmap_btalloc_write_stream", "xfs_bmap_write_stream_agno", "xfs_bmap_write_stream_rtbno", "fcntl_set_rw_hint" ], "Reasoning": "The patch series introduces generic write-stream fd management and integrates write stream allocation and hints into XFS and iomap. It adds new ioctls (FS_IOC_WRITE_STREAM_GET_MAX, FS_IOC_WRITE_STREAM_ALLOC, FS_IOC_WRITE_STREAM_SET), modifies fcntl write hint semantics, introduces anon-inode write-stream fds, and changes AG and realtime block allocation logic in XFS. All changes execute in core VFS/XFS code and are directly reachable from unprivileged/privileged userspace in standard virtualized environments.", "WorthFuzzing": true } Instruction: You are an expert Linux kernel maintainer and security engineer. Your job is to review a provided patch series and evaluate whether it warrants fuzzing with syzkaller. IMPORTANT: The changes have ALREADY been applied and committed as the HEAD commit in your workspace. Do NOT rely on internal assumptions. You must actively use your code access tools to inspect the actual source code, callers, and surrounding context. ================================================================================ 1. CORE TRIAGE PHILOSOPHY ================================================================================ The goal of patch fuzzing is to discover crashes, regressions, exposed latent bugs, and newly triggered assertions introduced by the patch series. - REACHABILITY IS THE PRIMARY GATE: Fuzzing can only discover bugs in code that can actually execute in standard virtualized environments (GCE or QEMU, utilizing software-emulated devices like USB gadgets, netdev, tun/tap). If the modified code is structurally unreachable (see Section 2), it MUST NOT be fuzzed, regardless of whether it adds assertions or complex logic. - DO NOT BLINDLY TRUST "NO FUNCTIONAL CHANGE" (NFCI) OR "REFACTORING" CLAIMS: Patch authors routinely label changes as "cleanups", "refactorings", or state "No functional change intended". Do NOT take these claims at face value. Code refactorings that rearrange logic, introduce helper functions, or alter state management in core subsystems frequently introduce subtle semantic shifts or uncover latent kernel bugs. If reachable executable code is modified or refactored, it MUST be fuzzed. - NEW OR MODIFIED ASSERTIONS IN REACHABLE CODE MUST BE FUZZED: When a patch introduces or modifies runtime checks or assertions (e.g., WARN_ON, VM_WARN_ON, BUG_ON, lockdep_assert) in reachable code paths, it enforces new or stricter invariants. Even if the author believes the invariant always holds, fuzzing is essential to verify whether an unusual sequence of operations can violate it. ================================================================================ 2. WHEN TO RETURN WorthFuzzing=false (NEGATIVE CRITERIA) ================================================================================ Return WorthFuzzing=false ONLY IF all modified code falls strictly into one or more of these categories: - Non-kernel and non-executable changes: * Modifications to Documentation/, comments, or spelling fixes. * User-space directories, self-tests, samples, or scripts (e.g., tools/, samples/, scripts/, usr/) that do not affect the compiled kernel image (vmlinux) or kernel modules. * Purely decorative logging (e.g., message strings in pr_err, printk, dev_info) or tracepoints that do not alter control flow or data structures. * Build system or Kconfig changes that do not alter compiled C logic. - Structurally unreachable hardware: * Vendor-specific PCIe switches, SmartNICs, or GPU drivers (e.g., mlxsw, pds_core, qed, ionic, amdgpu) requiring physical ASIC/PCIe cards not emulated in standard QEMU. - Unreachable execution paths: * Driver teardown callbacks (.remove, .shutdown, pci_unregister_driver) executed only during physical PCI hot-unplug or manual sysfs driver unbinding. * Code paths exclusive to architectures other than the target architecture. ================================================================================ 3. WHEN TO RETURN WorthFuzzing=true (POSITIVE CRITERIA) ================================================================================ Return WorthFuzzing=true whenever the patch touches reachable executable code, including: - Core Subsystems: * Any logic modifications in memory management (mm/), synchronization/locking (kernel/locking/), BPF, scheduler, core networking, VFS, or syscall handling. - Refactorings and Code Cleanups: * Any restructuring of reachable data structures, helper abstractions, or algorithm flows. - Runtime Assertions and Defensive Checks: * Any introduction or alteration of assertions (WARN_ON, VM_WARN_ON, BUG_ON, etc.) in reachable paths. - Reachable Drivers and Protocols: Drivers accessible via virtual buses (virtio, USB gadget, loopback, netlink, binder, sockets, etc.). ================================================================================ 4. EXTRACTING FocusSymbols (PREVENTING DILUTION) ================================================================================ When WorthFuzzing=true, you must extract specific kernel functions into FocusSymbols to guide the fuzzer: - AVOID UBIQUITOUS LIFECYCLE HOT-PATHS: Do NOT list generic, ubiquitous functions called by almost every program in the corpus (including, but not limited to: general memory allocators and deallocators, page fault and trap handlers, or core synchronization primitives; this is not an exhaustive list). Listing ubiquitous functions causes the fuzzer to classify thousands of unrelated tests as "focused", which severely dilutes fuzzing effort away from the actual changes. - TARGET SPECIFIC FEATURE LOGIC AND ENTRYPOINTS: List functions that specifically implement the logic being added or altered, or direct API entrypoints for the subsystem feature under review. - HANDLING STATIC INLINE FUNCTIONS IN HEADERS (.h): Compiler-inlined static functions (such as static inlines in mm/.h or include/linux/.h) lack distinct symbol addresses in vmlinux and cannot be targeted directly by symbol coverage filters. If the changes are primarily in static inline helpers, identify non-static, feature-specific caller functions in .c files that exercise them (avoiding ubiquitous lifecycle wrappers). ================================================================================ 5. IDENTIFYING EnableConfigs ================================================================================ Identify any specific CONFIG_ options required to properly compile and reach the modified code: - Inspect Kconfig files and #ifdef guards; do not make assumptions. - Check "depends on" lines in Kconfig to include any non-standard parent subsystem configs needed. - Strip any 'CONFIG_' prefix (e.g., return "NET_IPV4" instead of "CONFIG_NET_IPV4"). Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 86268a1e4affea45948924a7f9d04ec07de91884 Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 23 06:44:46 2026 +0000 syz-cluster: applied patch under review diff --git a/fs/Makefile b/fs/Makefile index 055dfc23d82b6..494da034cef2f 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -23,7 +23,7 @@ obj-$(CONFIG_PROC_FS) += proc_namespace.o obj-$(CONFIG_LEGACY_DIRECT_IO) += direct-io.o obj-y += notify/ obj-$(CONFIG_EPOLL) += eventpoll.o -obj-y += anon_inodes.o +obj-y += anon_inodes.o write_streams.o obj-$(CONFIG_SIGNALFD) += signalfd.o obj-$(CONFIG_TIMERFD) += timerfd.o obj-$(CONFIG_EVENTFD) += eventfd.o diff --git a/fs/fcntl.c b/fs/fcntl.c index c158f082f1da4..a5439e076197f 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -380,7 +380,14 @@ static long fcntl_set_rw_hint(struct file file, unsigned long arg) if (!rw_hint_valid(hint)) return -EINVAL; + / keep write stream and write life time hint mutually exclusive / + spin_lock(&inode->i_lock); + if (hint != WRITE_LIFE_NOT_SET && READ_ONCE(inode->i_write_stream)) { + spin_unlock(&inode->i_lock); + return -EBUSY; + } WRITE_ONCE(inode->i_write_hint, hint); + spin_unlock(&inode->i_lock); / * file->f_mapping->host may differ from inode. As an example, diff --git a/fs/inode.c b/fs/inode.c index ba7da39be4a31..50b91d449a384 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -246,6 +246,7 @@ int inode_init_always_gfp(struct super_block sb, struct inode inode, gfp_t gfp atomic_set(&inode->i_writecount, 0); inode->i_size = 0; inode->i_write_hint = WRITE_LIFE_NOT_SET; + inode->i_write_stream = 0; inode->i_blocks = 0; inode->i_bytes = 0; inode->i_generation = 0; diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 8b4039d16ce89..f406a7bc88043 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -349,6 +349,7 @@ static ssize_t iomap_dio_bio_iter_one(struct iomap_iter iter, fscrypt_set_bio_crypt_ctx(bio, iter->inode, pos, GFP_KERNEL); bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos); bio->bi_write_hint = iter->inode->i_write_hint; + bio->bi_write_stream = iter->iomap.write_stream; bio->bi_ioprio = dio->iocb->ki_ioprio; bio->bi_private = dio; bio->bi_end_io = iomap_dio_bio_end_io; diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c index 7bbbb417f9152..31a229c12b13d 100644 --- a/fs/iomap/ioend.c +++ b/fs/iomap/ioend.c @@ -166,6 +166,7 @@ static struct iomap_ioend iomap_alloc_ioend(struct iomap_writepage_ctx wpc, GFP_NOFS, &iomap_ioend_bioset); bio->bi_iter.bi_sector = iomap_sector(&wpc->iomap, pos); bio->bi_write_hint = wpc->inode->i_write_hint; + bio->bi_write_stream = wpc->iomap.write_stream; wbc_init_bio(wpc->wbc, bio); wpc->nr_folios = 0; return iomap_init_ioend(wpc->inode, bio, pos, ioend_flags); @@ -189,6 +190,8 @@ static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx wpc, loff_t pos, if (!(wpc->iomap.flags & IOMAP_F_ANON_WRITE) && iomap_sector(&wpc->iomap, pos) != bio_end_sector(&ioend->io_bio)) return false; + if (wpc->iomap.write_stream != ioend->io_bio.bi_write_stream) + return false; /* * Limit ioend bio chain lengths to minimise IO completion latency. This * also prevents long tight loops ending page writeback on all the diff --git a/fs/write_streams.c b/fs/write_streams.c new file mode 100644 index 0000000000000..b7f6ca6cf7250 --- /dev/null +++ b/fs/write_streams.c @@ -0,0 +1,138 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Generic write-stream fd management. / +#include <linux/anon_inodes.h> +#include <linux/bitmap.h> +#include <linux/err.h> +#include <linux/file.h> +#include <linux/fs.h> +#include <linux/mount.h> +#include <linux/slab.h> +#include <linux/write_streams.h> + +struct write_stream { + struct write_stream_pool pool; + struct vfsmount mnt; / pins the mount / + u16 id; / 1-based slot number / +}; + +static int write_stream_release(struct inode inode, struct file file) +{ + struct write_stream ws = file->private_data; + + spin_lock(&ws->pool->lock); + __clear_bit(ws->id - 1, ws->pool->streams_in_use); + spin_unlock(&ws->pool->lock); + mntput(ws->mnt); + kfree(ws); + return 0; +} + +static const struct file_operations write_stream_fops = { + .release = write_stream_release, + .llseek = noop_llseek, +}; + +/** + * write_stream_pool_init - size a write stream pool + * @pool: pool to initialise + * @nr: number of slots, may be zero + * + * Returns 0, or -ENOMEM if the bitmap cannot be allocated. + / +int write_stream_pool_init(struct write_stream_pool pool, unsigned int nr) +{ + spin_lock_init(&pool->lock); + pool->streams_in_use = NULL; + pool->nr_streams = 0; + + if (!nr) + return 0; + + pool->streams_in_use = bitmap_zalloc(nr, GFP_KERNEL); + if (!pool->streams_in_use) + return -ENOMEM; + pool->nr_streams = nr; + return 0; +} +EXPORT_SYMBOL_GPL(write_stream_pool_init); + +/** + * write_stream_pool_destroy - free a write stream pool + * @pool: pool to release + / +void write_stream_pool_destroy(struct write_stream_pool pool) +{ + bitmap_free(pool->streams_in_use); + pool->streams_in_use = NULL; + pool->nr_streams = 0; +} +EXPORT_SYMBOL_GPL(write_stream_pool_destroy); + +/** + * write_stream_alloc_fd - reserve a slot and return an fd naming it + * @pool: pool to reserve from + * @file: file whose mount is pinned for the life of the stream + * + * Returns an O_RDONLY \| O_CLOEXEC fd, -EOPNOTSUPP if the pool has no slots, + * or -EBUSY if they are all taken. + / +int write_stream_alloc_fd(struct write_stream_pool pool, struct file file) +{ + struct write_stream ws; + unsigned int slot; + int fd; + + if (!pool->nr_streams) + return -EOPNOTSUPP; + + ws = kzalloc_obj(ws, GFP_KERNEL); + if (!ws) + return -ENOMEM; + + spin_lock(&pool->lock); + slot = find_first_zero_bit(pool->streams_in_use, pool->nr_streams); + if (slot >= pool->nr_streams) { + spin_unlock(&pool->lock); + kfree(ws); + return -EBUSY; + } + __set_bit(slot, pool->streams_in_use); + spin_unlock(&pool->lock); + + ws->pool = pool; + ws->mnt = mntget(file->f_path.mnt); + ws->id = slot + 1; + + fd = anon_inode_getfd("[write_stream]", &write_stream_fops, ws, + O_RDONLY \| O_CLOEXEC); + if (fd < 0) { + spin_lock(&pool->lock); + __clear_bit(slot, pool->streams_in_use); + spin_unlock(&pool->lock); + mntput(ws->mnt); + kfree(ws); + } + return fd; +} +EXPORT_SYMBOL_GPL(write_stream_alloc_fd); + +/* + * write_stream_get_id - the id a stream file names + * @file: candidate stream file + * @pool: pool the stream must belong to, or NULL to accept any + * + * Returns the 1-based id, or -EINVAL if @file is not a stream file, or is + * a stream of a different pool. + / +int write_stream_get_id(struct file file, const struct write_stream_pool pool) +{ + struct write_stream ws; + + if (file->f_op != &write_stream_fops) + return -EINVAL; + ws = file->private_data; + if (pool && ws->pool != pool) + return -EINVAL; + return ws->id; +} +EXPORT_SYMBOL_GPL(write_stream_get_id); diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c index d64defeda645e..2e83811cefcbc 100644 --- a/fs/xfs/libxfs/xfs_bmap.c +++ b/fs/xfs/libxfs/xfs_bmap.c @@ -3579,8 +3579,31 @@ xfs_bmap_btalloc_filestreams( return xfs_bmap_btalloc_low_space(ap, args); } +static xfs_agnumber_t +xfs_bmap_write_stream_agno( + struct xfs_inode ip, + unsigned int stream_id) +{ + struct xfs_mount mp = ip->i_mount; + xfs_agnumber_t nr_ags = mp->m_sb.sb_agcount; + unsigned int nr_streams = + write_stream_pool_count(&mp->m_ddev_targp->bt_stream_pool); + xfs_agnumber_t ag_set_size, start_agno; + + stream_id -= 1; /* convert from 1-based to 0-based / + ag_set_size = nr_ags / nr_streams; + start_agno = stream_id ag_set_size; + + /* last stream absorbs any uneven remainder / + if (stream_id == nr_streams - 1) + ag_set_size = nr_ags - start_agno; + + return start_agno + I_INO(ip) % ag_set_size; +} + +/ Core AG allocator. The caller sets ap->blkno to the target AG start. / static int -xfs_bmap_btalloc_best_length( +xfs_bmap_btalloc_from_blkno( struct xfs_bmalloca ap, struct xfs_alloc_arg args, int stripe_align) @@ -3588,7 +3611,6 @@ xfs_bmap_btalloc_best_length( xfs_extlen_t blen = 0; int error; - ap->blkno = XFS_INODE_TO_FSB(ap->ip); if (!xfs_bmap_adjacent(ap)) ap->eof = false; @@ -3621,6 +3643,32 @@ xfs_bmap_btalloc_best_length( return xfs_bmap_btalloc_low_space(ap, args); } +/ Start a write-stream file in the AG set that backs its stream. / +static int +xfs_bmap_btalloc_write_stream( + struct xfs_bmalloca ap, + struct xfs_alloc_arg args, + int stripe_align, + unsigned int stream_id) +{ + struct xfs_mount mp = ap->ip->i_mount; + xfs_agnumber_t agno; + + agno = xfs_bmap_write_stream_agno(ap->ip, stream_id); + ap->blkno = XFS_AGB_TO_FSB(mp, agno, 0); + return xfs_bmap_btalloc_from_blkno(ap, args, stripe_align); +} + +static int +xfs_bmap_btalloc_best_length( + struct xfs_bmalloca ap, + struct xfs_alloc_arg args, + int stripe_align) +{ + ap->blkno = XFS_INODE_TO_FSB(ap->ip); + return xfs_bmap_btalloc_from_blkno(ap, args, stripe_align); +} + static int xfs_bmap_btalloc( struct xfs_bmalloca ap) @@ -3640,6 +3688,7 @@ xfs_bmap_btalloc( }; xfs_fileoff_t orig_offset; xfs_extlen_t orig_length; + unsigned int stream_id; int error; int stripe_align; @@ -3652,11 +3701,16 @@ xfs_bmap_btalloc( / Trim the allocation back to the maximum an AG can fit. / args.maxlen = min(ap->length, mp->m_ag_max_usable); + stream_id = READ_ONCE(VFS_I(ap->ip)->i_write_stream); + if (unlikely(XFS_TEST_ERROR(mp, XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT))) error = xfs_bmap_exact_minlen_extent_alloc(ap, &args); else if ((ap->datatype & XFS_ALLOC_USERDATA) && xfs_inode_is_filestream(ap->ip)) error = xfs_bmap_btalloc_filestreams(ap, &args, stripe_align); + else if ((ap->datatype & XFS_ALLOC_USERDATA) && stream_id) + error = xfs_bmap_btalloc_write_stream(ap, &args, stripe_align, + stream_id); else error = xfs_bmap_btalloc_best_length(ap, &args, stripe_align); if (error) diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c index 8256c1d13ce20..1748be9aa7d65 100644 --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -1647,6 +1647,7 @@ void xfs_free_buftarg( struct xfs_buftarg btp) { + write_stream_pool_destroy(&btp->bt_stream_pool); xfs_destroy_buftarg(btp); fs_put_dax(btp->bt_daxdev, btp->bt_mount); /* the main block device is closed by kill_block_super / @@ -1684,6 +1685,40 @@ xfs_configure_buftarg_atomic_writes( btp->bt_awu_max = max_bytes; } +#define XFS_MAX_SW_WRITE_STREAMS U8_MAX + +/ Heuristic to derive software write stream count from a group topology / +static unsigned int +xfs_sw_write_stream_count( + unsigned int nr_groups) +{ + unsigned int group_set_size; + + if (nr_groups >= 16) + group_set_size = 4; + else if (nr_groups >= 8) + group_set_size = 2; + else + group_set_size = 1; + return min(nr_groups / group_set_size, XFS_MAX_SW_WRITE_STREAMS); +} + +int +xfs_buftarg_init_streams( + struct xfs_buftarg btp, + unsigned int nr_groups) +{ + unsigned int nr_streams; + unsigned int hw_streams; + + hw_streams = bdev_max_write_streams(btp->bt_bdev); + if (hw_streams) + nr_streams = min(hw_streams, nr_groups); + else + nr_streams = xfs_sw_write_stream_count(nr_groups); + return write_stream_pool_init(&btp->bt_stream_pool, nr_streams); +} + /* Configure a buffer target that abstracts a block device. / int xfs_configure_buftarg( diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h index a4729253b56fd..b5292e5731e38 100644 --- a/fs/xfs/xfs_buf.h +++ b/fs/xfs/xfs_buf.h @@ -15,6 +15,7 @@ #include <linux/uio.h> #include <linux/list_lru.h> #include <linux/lockref.h> +#include <linux/write_streams.h> extern struct kmem_cache xfs_buf_cache; @@ -102,6 +103,9 @@ struct xfs_buftarg { unsigned int bt_awu_min; unsigned int bt_awu_max; + /* slot pool for stream fds on this device / + struct write_stream_pool bt_stream_pool; + struct rhashtable bt_hash; }; @@ -360,6 +364,8 @@ extern void xfs_buftarg_wait(struct xfs_buftarg ); extern void xfs_buftarg_drain(struct xfs_buftarg ); int xfs_configure_buftarg(struct xfs_buftarg btp, unsigned int sectorsize, xfs_fsblock_t nr_blocks); +int xfs_buftarg_init_streams(struct xfs_buftarg btp, + unsigned int nr_groups); #define xfs_readonly_buftarg(buftarg) bdev_read_only((buftarg)->bt_bdev) diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 030a7c8f2c129..c3503fe870bad 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -4,6 +4,7 @@ All Rights Reserved. / #include <linux/iversion.h> +#include <linux/write_streams.h> #include "xfs_platform.h" #include "xfs_fs.h" @@ -47,6 +48,74 @@ struct kmem_cache xfs_inode_cache; +/* Number of write streams available to this inode. / +int +xfs_inode_max_write_streams( + struct xfs_inode ip) +{ + xfs_assert_ilocked(ip, XFS_ILOCK_SHARED \| XFS_ILOCK_EXCL); + + if (xfs_inode_is_filestream(ip)) + return 0; + if (XFS_IS_REALTIME_INODE(ip) && xfs_has_zoned(ip->i_mount)) + return 0; + return write_stream_pool_count(&xfs_inode_buftarg(ip)->bt_stream_pool); +} + +/* Bind the write stream named by @stream_fd to @ip / +int +xfs_inode_set_write_stream( + struct xfs_inode ip, + int stream_fd) +{ + CLASS(fd, f)(stream_fd); + struct xfs_buftarg target; + int id, error = 0; + + if (!fd_file(f)) + return -EBADF; + xfs_ilock(ip, XFS_ILOCK_EXCL); + if (XFS_IS_REALTIME_INODE(ip) && xfs_has_zoned(ip->i_mount)) { + error = -EINVAL; + goto out_unlock; + } + + target = xfs_inode_buftarg(ip); + id = write_stream_get_id(fd_file(f), &target->bt_stream_pool); + if (id < 0) { + error = id; + goto out_unlock; + } + + / Filestream and write-stream are mutually exclusive / + if (xfs_inode_is_filestream(ip)) { + error = -EINVAL; + goto out_unlock; + } + + / keep write stream and write life time hint mutually exclusive / + spin_lock(&VFS_I(ip)->i_lock); + if (VFS_I(ip)->i_write_hint != WRITE_LIFE_NOT_SET) { + spin_unlock(&VFS_I(ip)->i_lock); + error = -EBUSY; + goto out_unlock; + } + WRITE_ONCE(VFS_I(ip)->i_write_stream, id); + spin_unlock(&VFS_I(ip)->i_lock); +out_unlock: + xfs_iunlock(ip, XFS_ILOCK_EXCL); + return error; +} + +void +xfs_inode_clear_write_stream( + struct xfs_inode ip) +{ + xfs_ilock(ip, XFS_ILOCK_EXCL); + WRITE_ONCE(VFS_I(ip)->i_write_stream, 0); + xfs_iunlock(ip, XFS_ILOCK_EXCL); +} + /* * These two are wrapper routines around the xfs_ilock() routine used to * centralize some grungy code. They are used in places that wish to lock the diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h index 1602027cd0aa5..c053f105d2fa8 100644 --- a/fs/xfs/xfs_inode.h +++ b/fs/xfs/xfs_inode.h @@ -672,4 +672,8 @@ int xfs_icreate_dqalloc(const struct xfs_icreate_args args, struct xfs_dquot udqpp, struct xfs_dquot gdqpp, struct xfs_dquot pdqpp); +int xfs_inode_max_write_streams(struct xfs_inode ip); +int xfs_inode_set_write_stream(struct xfs_inode ip, int stream_fd); +void xfs_inode_clear_write_stream(struct xfs_inode ip); + #endif /* __XFS_INODE_H__ / diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c index 96ca3e480cb9f..4c0aff34e3c3d 100644 --- a/fs/xfs/xfs_ioctl.c +++ b/fs/xfs/xfs_ioctl.c @@ -557,6 +557,12 @@ xfs_ioctl_setattr_xflags( bool rtflag = (fa->fsx_xflags & FS_XFLAG_REALTIME); uint64_t i_flags2; + / refuse a filestream/realtime flag change while a stream is attached / + if (READ_ONCE(VFS_I(ip)->i_write_stream) && + ((fa->fsx_xflags & FS_XFLAG_FILESTREAM) \|\| + rtflag != XFS_IS_REALTIME_INODE(ip))) + return -EINVAL; + if (rtflag != XFS_IS_REALTIME_INODE(ip)) { / Can't change realtime flag if any extents are allocated. / if (xfs_inode_has_filedata(ip)) @@ -1200,6 +1206,73 @@ xfs_ioctl_fs_counts( return 0; } +static int +xfs_ioc_write_stream_get_max( + struct file filp, + void __user arg) +{ + struct xfs_inode ip = XFS_I(file_inode(filp)); + __u32 max; + + xfs_ilock(ip, XFS_ILOCK_SHARED); + max = xfs_inode_max_write_streams(ip); + xfs_iunlock(ip, XFS_ILOCK_SHARED); + + return put_user(max, (__u32 __user )arg); +} + +static int +xfs_ioc_write_stream_alloc( + struct file filp) +{ + struct xfs_inode ip = XFS_I(file_inode(filp)); + struct xfs_buftarg target; + int max; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + xfs_ilock(ip, XFS_ILOCK_SHARED); + max = xfs_inode_max_write_streams(ip); + target = xfs_inode_buftarg(ip); + xfs_iunlock(ip, XFS_ILOCK_SHARED); + + if (!max) + return -EOPNOTSUPP; + return write_stream_alloc_fd(&target->bt_stream_pool, filp); +} + +static int +xfs_ioc_write_stream_set( + struct file filp, + void __user arg) +{ + struct xfs_inode ip = XFS_I(file_inode(filp)); + struct fs_write_stream_set set; + + if (!(filp->f_mode & FMODE_WRITE)) + return -EBADF; + if (copy_from_user(&set, arg, sizeof(set))) + return -EFAULT; + if (set.flags & ~FS_WRITE_STREAM_SET_CLEAR) + return -EINVAL; + + / Regular files only. / + if (!S_ISREG(VFS_I(ip)->i_mode)) + return -EINVAL; + + if (!inode_owner_or_capable(file_mnt_idmap(filp), VFS_I(ip))) + return -EPERM; + + if (set.flags & FS_WRITE_STREAM_SET_CLEAR) { + if (set.stream_fd != -1) + return -EINVAL; + xfs_inode_clear_write_stream(ip); + return 0; + } + return xfs_inode_set_write_stream(ip, set.stream_fd); +} + / * These long-unused ioctls were removed from the official ioctl API in 5.17, * but retain these definitions so that we can log warnings about them. @@ -1466,6 +1539,13 @@ xfs_file_ioctl( case XFS_IOC_VERIFY_MEDIA: return xfs_ioc_verify_media(filp, arg); + case FS_IOC_WRITE_STREAM_GET_MAX: + return xfs_ioc_write_stream_get_max(filp, arg); + case FS_IOC_WRITE_STREAM_ALLOC: + return xfs_ioc_write_stream_alloc(filp); + case FS_IOC_WRITE_STREAM_SET: + return xfs_ioc_write_stream_set(filp, (void __user )arg); + default: return -ENOTTY; } diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 7c6238fed61e4..3e9df790a544e 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -144,6 +144,7 @@ xfs_bmbt_to_iomap( } iomap->offset = XFS_FSB_TO_B(mp, imap->br_startoff); iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount); + iomap->write_stream = READ_ONCE(VFS_I(ip)->i_write_stream); if (mapping_flags & IOMAP_DAX) { iomap->dax_dev = target->bt_daxdev; } else { diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c index 84efe5a8fb11d..a291f1aca6eb4 100644 --- a/fs/xfs/xfs_rtalloc.c +++ b/fs/xfs/xfs_rtalloc.c @@ -2160,6 +2160,28 @@ xfs_rtallocate_align( return 0; } +static xfs_rtblock_t +xfs_bmap_write_stream_rtbno( + struct xfs_inode ip, + unsigned int stream_id) +{ + struct xfs_mount mp = ip->i_mount; + unsigned int nr_rtgs = mp->m_sb.sb_rgcount; + unsigned int nr_streams = + write_stream_pool_count(&mp->m_rtdev_targp->bt_stream_pool); + unsigned int set_size = nr_rtgs / nr_streams; + xfs_rgnumber_t start_rgno, target_rgno; + + stream_id -= 1; / convert from 1-based to 0-based / + start_rgno = stream_id set_size; + if (stream_id == nr_streams - 1) + set_size = nr_rtgs - start_rgno; + target_rgno = start_rgno + I_INO(ip) % set_size; + + return (xfs_rtblock_t)target_rgno << + mp->m_groups[XG_TYPE_RTG].blklog; +} + int xfs_bmap_rtalloc( struct xfs_bmalloca ap) @@ -2174,10 +2196,13 @@ xfs_bmap_rtalloc( bool noalign = false; bool initial_user_data = ap->datatype & XFS_ALLOC_INITIAL_USER_DATA; + unsigned int stream_id; int error; ASSERT(!xfs_has_zoned(ap->tp->t_mountp)); + stream_id = READ_ONCE(VFS_I(ap->ip)->i_write_stream); + retry: error = xfs_rtallocate_align(ap, &ralen, &raminlen, &prod, &noalign); if (error) @@ -2185,6 +2210,8 @@ xfs_bmap_rtalloc( if (xfs_bmap_adjacent(ap)) bno_hint = ap->blkno; + else if (stream_id && xfs_has_rtgroups(ap->ip->i_mount)) + bno_hint = xfs_bmap_write_stream_rtbno(ap->ip, stream_id); if (xfs_has_rtgroups(ap->ip->i_mount)) { error = xfs_rtallocate_rtgs(ap->tp, bno_hint, raminlen, ralen, diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index b24db75eaedc5..5c92f8ebd8a73 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -608,6 +608,11 @@ xfs_setup_devices( if (error) return error; + error = xfs_buftarg_init_streams(mp->m_ddev_targp, + mp->m_sb.sb_agcount); + if (error) + return error; + if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp) { unsigned int log_sector_size = BBSIZE; @@ -632,6 +637,13 @@ xfs_setup_devices( if (error) return error; xfs_update_bdi_rahead(mp); + + if (xfs_has_rtgroups(mp) && !xfs_has_zoned(mp)) { + error = xfs_buftarg_init_streams(mp->m_rtdev_targp, + mp->m_sb.sb_rgcount); + if (error) + return error; + } } return 0; diff --git a/include/linux/fs.h b/include/linux/fs.h index f9d1e05e8ae68..3d9ce4d30cd54 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -812,7 +812,7 @@ struct inode { / Misc / struct inode_state_flags i_state; - / 32-bit hole / + u16 i_write_stream; struct rw_semaphore i_rwsem; unsigned long dirtied_when; / jiffies of first dirtying / diff --git a/include/linux/iomap.h b/include/linux/iomap.h index bc7ae6327dbf8..f923778f08bd7 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -133,6 +133,7 @@ struct iomap { u64 length; / length of mapping, bytes / u16 type; / type of mapping / u16 flags; / flags for mapping / + u16 write_stream; / write stream for I/O / struct block_device bdev; /* block device for I/O / struct dax_device dax_dev; /* dax_dev for dax operations / void inline_data; diff --git a/include/linux/write_streams.h b/include/linux/write_streams.h new file mode 100644 index 0000000000000..d27f42df59845 --- /dev/null +++ b/include/linux/write_streams.h @@ -0,0 +1,33 @@ +/* SPDX-License-Identifier: GPL-2.0 / +#ifndef _LINUX_WRITE_STREAMS_H +#define _LINUX_WRITE_STREAMS_H + +#include <linux/spinlock.h> +#include <linux/types.h> + +struct file; + +/ + * Write stream slot pool, embedded in whatever filesystem object scopes + * an id space. + / +struct write_stream_pool { + unsigned int nr_streams; + unsigned long streams_in_use; + spinlock_t lock; +}; + +static inline unsigned int +write_stream_pool_count(const struct write_stream_pool pool) +{ + return pool->nr_streams; +} + +int write_stream_pool_init(struct write_stream_pool pool, unsigned int nr); +void write_stream_pool_destroy(struct write_stream_pool pool); + +int write_stream_alloc_fd(struct write_stream_pool pool, struct file file); +int write_stream_get_id(struct file file, + const struct write_stream_pool pool); + +#endif / _LINUX_WRITE_STREAMS_H / diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 34c6f219462a5..1974052aa476b 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -345,6 +345,21 @@ struct file_attr { / Get logical block metadata capability details / #define FS_IOC_GETLBMD_CAP _IOWR(0x15, 2, struct logical_block_metadata_cap) +struct fs_write_stream_set { + __s32 stream_fd; / IN: stream to attach, -1 to clear / + __u32 flags; / IN: FS_WRITE_STREAM_SET_* / +}; + +/ Clear the file's write stream. Requires stream_fd to be -1. / +#define FS_WRITE_STREAM_SET_CLEAR (1U << 0) + +/ GET_MAX returns the count through its argument; ALLOC returns a stream fd + * as the ioctl return value and takes none. + / +#define FS_IOC_WRITE_STREAM_GET_MAX _IOR(0x15, 3, __u32) +#define FS_IOC_WRITE_STREAM_ALLOC _IO(0x15, 4) +#define FS_IOC_WRITE_STREAM_SET _IOW(0x15, 5, struct fs_write_stream_set) + / * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS) *
3/2	2026/09/23 06:44	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 13397 output: 29 thoughts: 1350 Thoughts: Kernel Patch Evaluation: Write Streams for XFS Okay, so the task is to determine if this kernel patch series warrants fuzzing with syzkaller. First, I need to understand the evaluation criteria, so let me quickly review the core triage philosophy. The most important thing is reachability – can the code execute in a standard virtualized environment? I need to look closely to make sure any claims of "no functional change" or "refactoring" are not misleading. New or modified assertions in reachable code are definitely targets for fuzzing. If something's unreachable due to hardware restrictions or code paths that only execute during driver teardown or on other architectures, then it's not a fuzzing candidate. Core subsystems, refactorings in reachable code, runtime assertions, reachable drivers and protocols – these are all good indicators for fuzzing. I also need to be aware of how to construct a useful `FocusSymbols` list to avoid diluted coverage, targeting specific features and entry points, also consider static inlines, and note any required Kernel Configs. Alright, let's dive into this patch. I see new files and changes across several directories: `fs/Makefile`, `fs/fcntl.c`, `fs/inode.c`, `fs/iomap/direct-io.c`, `fs/iomap/ioend.c`, `fs/write_streams.c`, along with many files related to XFS (`fs/xfs/libxfs/`, `fs/xfs/xfs_buf.c`, `fs/xfs/xfs_inode.c`, `fs/xfs/xfs_ioctl.c`, `fs/xfs/xfs_iomap.c`, `fs/xfs/xfs_rtalloc.c`, `fs/xfs/xfs_super.c`). And importantly, I see header changes in `include/linux/fs.h`, `include/linux/iomap.h`, `include/linux/write_streams.h`, and `include/uapi/linux/fs.h`. This seems quite promising. The introduction of `write_streams.c` for generic write-stream fd management, the modifications within XFS, the new ioctls (FS_IOC_WRITE_STREAM_ALLOC, FS_IOC_WRITE_STREAM_SET, FS_IOC_WRITE_STREAM_GET_MAX), and the hooks in XFS block allocation and iomap writes… all of this is definitely reachable in standard virtualized environments. I can mount XFS filesystems in QEMU or GCE using loopback, virtio-blk, or a ramdisk. Userspace can then interact with the new ioctls and file operations on write_stream anon inode. Thus, `WorthFuzzing` is definitely `TRUE`. Now, I need to figure out the specific configs and focus symbols. Since `fs/write_streams.c` is compiled unconditionally (`obj-y += anon_inodes.o write_streams.o`) but this patch touches XFS, I need to check the Kconfig files or use `grepper` to see what configuration flags, besides `CONFIG_XFS_FS`, may be necessary for the new or modified XFS functionality.
4/2	2026/09/23 06:45	tool	grepper	0m Args: { "Expression": "config XFS_FS", "PathPrefix": "fs/xfs" } Results: { "Output": "fs/xfs/Kconfig-1-# SPDX-License-Identifier: GPL-2.0-only\nfs/xfs/Kconfig:2:config XFS_FS\nfs/xfs/Kconfig-3-\ttristate \"XFS filesystem support\"\n" }
5/2	2026/09/23 06:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 15539 output: 34 thoughts: 45 Thoughts: Okay, let's dive into this. Examining XFS Configuration Options Alright, my first instinct is to zero in on the `fs/xfs/Kconfig` file. That's the logical place to start when exploring XFS configuration options. I need to refresh my memory and see what choices we have. I'm particularly interested in anything related to realtime functionality, so `CONFIG_XFS_RT` jumps out as a potential candidate to investigate further. Time to crack open `fs/xfs/Kconfig` and take a look.
6/2	2026/09/23 06:45	tool	read-file	0m Args: { "File": "fs/xfs/Kconfig", "FirstLine": 1, "LineCount": 100 } Results: { "Contents": " 1:\t# SPDX-License-Identifier: GPL-2.0-only\n 2:\tconfig XFS_FS\n 3:\t\ttristate \"XFS filesystem support\"\n 4:\t\tdepends on BLOCK\n 5:\t\tselect EXPORTFS\n 6:\t\tselect CRC32\n 7:\t\tselect FS_IOMAP\n 8:\t\thelp\n 9:\t\t XFS is a high performance journaling filesystem which originated\n 10:\t\t on the SGI IRIX platform. It is completely multi-threaded, can\n 11:\t\t support large files and large filesystems, extended attributes,\n 12:\t\t variable block sizes, is extent based, and makes extensive use of\n 13:\t\t Btrees (directories, extents, free space) to aid both performance\n 14:\t\t and scalability.\n 15:\t\n 16:\t\t Refer to the documentation at \u003chttp://oss.sgi.com/projects/xfs/\u003e\n 17:\t\t for complete details. This implementation is on-disk compatible\n 18:\t\t with the IRIX version of XFS.\n 19:\t\n 20:\t\t To compile this file system support as a module, choose M here: the\n 21:\t\t module will be called xfs. Be aware, however, that if the file\n 22:\t\t system of your root partition is compiled as a module, you'll need\n 23:\t\t to use an initial ramdisk (initrd) to boot.\n 24:\t\n 25:\tconfig XFS_SUPPORT_V4\n 26:\t\tbool \"Support deprecated V4 (crc=0) format\"\n 27:\t\tdepends on XFS_FS\n 28:\t\tdefault n\n 29:\t\thelp\n 30:\t\t The V4 filesystem format lacks certain features that are supported\n 31:\t\t by the V5 format, such as metadata checksumming, strengthened\n 32:\t\t metadata verification, and the ability to store timestamps past the\n 33:\t\t year 2038. Because of this, the V4 format is deprecated. All users\n 34:\t\t should upgrade by backing up their files, reformatting, and restoring\n 35:\t\t from the backup.\n 36:\t\n 37:\t\t Administrators and users can detect a V4 filesystem by running\n 38:\t\t xfs_info against a filesystem mountpoint and checking for a string\n 39:\t\t beginning with \"crc=\". If the string \"crc=0\" is found, the\n 40:\t\t filesystem is a V4 filesystem. If no such string is found, please\n 41:\t\t upgrade xfsprogs to the latest version and try again.\n 42:\t\n 43:\t\t This option became default N in September 2025. Support for the\n 44:\t\t V4 format will be removed entirely in September 2030. Distributors\n 45:\t\t can say N here to withdraw support earlier.\n 46:\t\n 47:\t\t To continue supporting the old V4 format (crc=0), say Y.\n 48:\t\t To close off an attack surface, say N.\n 49:\t\n 50:\tconfig XFS_SUPPORT_ASCII_CI\n 51:\t\tbool \"Support deprecated case-insensitive ascii (ascii-ci=1) format\"\n 52:\t\tdepends on XFS_FS\n 53:\t\tdefault n\n 54:\t\thelp\n 55:\t\t The ASCII case insensitivity filesystem feature only works correctly\n 56:\t\t on systems that have been coerced into using ISO 8859-1, and it does\n 57:\t\t not work on extended attributes. The kernel has no visibility into\n 58:\t\t the locale settings in userspace, so it corrupts UTF-8 names.\n 59:\t\t Enabling this feature makes XFS vulnerable to mixed case sensitivity\n 60:\t\t attacks. Because of this, the feature is deprecated. All users\n 61:\t\t should upgrade by backing up their files, reformatting, and restoring\n 62:\t\t from the backup.\n 63:\t\n 64:\t\t Administrators and users can detect such a filesystem by running\n 65:\t\t xfs_info against a filesystem mountpoint and checking for a string\n 66:\t\t beginning with \"ascii-ci=\". If the string \"ascii-ci=1\" is found, the\n 67:\t\t filesystem is a case-insensitive filesystem. If no such string is\n 68:\t\t found, please upgrade xfsprogs to the latest version and try again.\n 69:\t\n 70:\t\t This option became default N in September 2025. Support for the\n 71:\t\t feature will be removed entirely in September 2030. Distributors\n 72:\t\t can say N here to withdraw support earlier.\n 73:\t\n 74:\t\t To continue supporting case-insensitivity (ascii-ci=1), say Y.\n 75:\t\t To close off an attack surface, say N.\n 76:\t\n 77:\tconfig XFS_QUOTA\n 78:\t\tbool \"XFS Quota support\"\n 79:\t\tdepends on XFS_FS\n 80:\t\tselect QUOTACTL\n 81:\t\thelp\n 82:\t\t If you say Y here, you will be able to set limits for disk usage on\n 83:\t\t a per user and/or a per group basis under XFS. XFS considers quota\n 84:\t\t information as filesystem metadata and uses journaling to provide a\n 85:\t\t higher level guarantee of consistency. The on-disk data format for\n 86:\t\t quota is also compatible with the IRIX version of XFS, allowing a\n 87:\t\t filesystem to be migrated between Linux and IRIX without any need\n 88:\t\t for conversion.\n 89:\t\n 90:\t\t If unsure, say N. More comprehensive documentation can be found in\n 91:\t\t README.quota in the xfsprogs package. XFS quota can be used either\n 92:\t\t with or without the generic quota support enabled (CONFIG_QUOTA) -\n 93:\t\t they are completely independent subsystems.\n 94:\t\n 95:\tconfig XFS_POSIX_ACL\n 96:\t\tbool \"XFS POSIX ACL support\"\n 97:\t\tdepends on XFS_FS\n 98:\t\tselect FS_POSIX_ACL\n 99:\t\thelp\n 100:\t\t POSIX Access Control Lists (ACLs) support permissions for users and\n" }
7/2	2026/09/23 06:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 17360 output: 35 thoughts: 16 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience and presented in the first person: XFS Kconfig Deep Dive Alright, so I'm thinking, let's not just glance at the XFS configuration file and move on. We need to be thorough. The big picture is important, but often the devil is in the details, so a quick check of `fs/xfs/Kconfig` is in order. We should make sure we understand all aspects of the configuration options. Are there new, possibly subtle, dependencies that might impact performance or compatibility? Have any recent changes been made that require closer scrutiny? I'm imagining a complete, up-to-date overview of every option available to us; what the defaults are, which are critical, and which are useful under different circumstances. I'm after a solid baseline for knowing what's possible, what's sensible, and what to be wary of when tuning XFS for a specific workload or hardware configuration. We are experts, and only a deeper dive will satisfy!
8/2	2026/09/23 06:45	tool	read-file	0m Args: { "File": "fs/xfs/Kconfig", "FirstLine": 101, "LineCount": 80 } Results: { "Contents": " 101:\t\t groups beyond the owner/group/world scheme.\n 102:\t\n 103:\t\t If you don't know what Access Control Lists are, say N.\n 104:\t\n 105:\tconfig XFS_RT\n 106:\t\tbool \"XFS Realtime subvolume support\"\n 107:\t\tdepends on XFS_FS\n 108:\t\tdefault BLK_DEV_ZONED\n 109:\t\thelp\n 110:\t\t If you say Y here you will be able to mount and use XFS filesystems\n 111:\t\t which contain a realtime subvolume. The realtime subvolume is a\n 112:\t\t separate area of disk space where only file data is stored. It was\n 113:\t\t originally designed to provide deterministic data rates suitable\n 114:\t\t for media streaming applications, but is also useful as a generic\n 115:\t\t mechanism for ensuring data and metadata/log I/Os are completely\n 116:\t\t separated. Regular file I/Os are isolated to a separate device\n 117:\t\t from all other requests, and this can be done quite transparently\n 118:\t\t to applications via the inherit-realtime directory inode flag.\n 119:\t\n 120:\t\t See the xfs man page in section 5 for additional information.\n 121:\t\n 122:\t\t This option is mandatory to support zoned block devices. For these\n 123:\t\t devices, the realtime subvolume must be backed by a zoned block\n 124:\t\t device and a regular block device used as the main device (for\n 125:\t\t metadata). If the zoned block device is a host-managed SMR hard-disk\n 126:\t\t containing conventional zones at the beginning of its address space,\n 127:\t\t XFS will use the disk conventional zones as the main device and the\n 128:\t\t remaining sequential write required zones as the backing storage for\n 129:\t\t the realtime subvolume.\n 130:\t\n 131:\t\t If unsure, say N.\n 132:\t\n 133:\tconfig XFS_DRAIN_INTENTS\n 134:\t\tbool\n 135:\t\tselect JUMP_LABEL if HAVE_ARCH_JUMP_LABEL\n 136:\t\n 137:\tconfig XFS_LIVE_HOOKS\n 138:\t\tbool\n 139:\t\tselect JUMP_LABEL if HAVE_ARCH_JUMP_LABEL\n 140:\t\n 141:\tconfig XFS_MEMORY_BUFS\n 142:\t\tbool\n 143:\t\n 144:\tconfig XFS_BTREE_IN_MEM\n 145:\t\tbool\n 146:\t\n 147:\tconfig XFS_ONLINE_SCRUB\n 148:\t\tbool \"XFS online metadata check support\"\n 149:\t\tdefault y\n 150:\t\tdepends on XFS_FS\n 151:\t\tdepends on TMPFS \u0026\u0026 SHMEM\n 152:\t\tselect XFS_LIVE_HOOKS\n 153:\t\tselect XFS_DRAIN_INTENTS\n 154:\t\tselect XFS_MEMORY_BUFS\n 155:\t\thelp\n 156:\t\t If you say Y here you will be able to check metadata on a\n 157:\t\t mounted XFS filesystem. This feature is intended to reduce\n 158:\t\t filesystem downtime by supplementing xfs_repair. The key\n 159:\t\t advantage here is to look for problems proactively so that\n 160:\t\t they can be dealt with in a controlled manner.\n 161:\t\n 162:\t\t See the xfs_scrub man page in section 8 for additional information.\n 163:\t\n 164:\tconfig XFS_ONLINE_SCRUB_STATS\n 165:\t\tbool \"XFS online metadata check usage data collection\"\n 166:\t\tdefault y\n 167:\t\tdepends on XFS_ONLINE_SCRUB\n 168:\t\tdepends on DEBUG_FS\n 169:\t\thelp\n 170:\t\t If you say Y here, the kernel will gather usage data about\n 171:\t\t the online metadata check subsystem. This includes the number\n 172:\t\t of invocations, the outcomes, and the results of repairs, if any.\n 173:\t\t This may slow down scrub slightly due to the use of high precision\n 174:\t\t timers and the need to merge per-invocation information into the\n 175:\t\t filesystem counters.\n 176:\t\n 177:\t\t Usage data are collected in /sys/kernel/debug/xfs/scrub.\n 178:\t\n 179:\tconfig XFS_ONLINE_REPAIR\n 180:\t\tbool \"XFS online metadata repair support\"\n" }
9/2	2026/09/23 06:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 18872 output: 29 thoughts: 233 Thoughts: Analyzing XFS Real-Time Allocation Code Okay, so I'm looking at this XFS patch and immediately my attention is drawn to these specific sections in `xfs_rtalloc.c`: `xfs_bmap_write_stream_rtbno` and `xfs_bmap_rtalloc`. I see that `xfs_bmap_write_stream_rtbno` is used when dealing with streams and Real-Time groups, which makes sense given the file's name. Specifically, there's this conditional: `else if (stream_id && xfs_has_rtgroups(ap->ip->i_mount))`. That makes perfect sense; if we have a stream and RT groups, we get the real-time block number hint. Then, over in `xfs_super.c`, there's this part that's relevant to stream initialization: `if (xfs_has_rtgroups(mp) && !xfs_has_zoned(mp))`. It seems we're initializing streams for RT groups unless we have zoned storage. Interesting. Now, a red flag goes up. `xfs_rtalloc.c` is only built if the kernel is configured with `CONFIG_XFS_RT`. This means there's a strong dependency on the real-time configuration. I should probably go back and look at `fs/xfs/Makefile` to confirm the conditional compilation. Just need to double-check that this dependency is managed correctly.
10/2	2026/09/23 06:45	tool	grepper	0m Args: { "Expression": "xfs_rtalloc", "PathPrefix": "fs/xfs" } Results: { "Output": "\nFull output is too long, showing 500 out of 635 lines.\nUse more precise expression if possible.\n\nfs/xfs/Makefile=134=xfs-$(CONFIG_XFS_QUOTA)\t\t+= xfs_dquot.o \\\n--\nfs/xfs/Makefile-142-# xfs_rtbitmap is shared with libxfs\nfs/xfs/Makefile:143:xfs-$(CONFIG_XFS_RT)\t\t+= xfs_rtalloc.o \\\nfs/xfs/Makefile-144-\t\t\t\t xfs_zone_alloc.o \\\n--\nfs/xfs/libxfs/xfs_refcount.c-28-#include \"xfs_rtgroup.h\"\nfs/xfs/libxfs/xfs_refcount.c:29:#include \"xfs_rtalloc.h\"\nfs/xfs/libxfs/xfs_refcount.c-30-#include \"xfs_rtrefcount_btree.h\"\n--\nfs/xfs/libxfs/xfs_rtbitmap.c-18-#include \"xfs_trans.h\"\nfs/xfs/libxfs/xfs_rtbitmap.c:19:#include \"xfs_rtalloc.h\"\nfs/xfs/libxfs/xfs_rtbitmap.c-20-#include \"xfs_error.h\"\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=130=xfs_rtbuf_cache_relse(\nfs/xfs/libxfs/xfs_rtbitmap.c:131:\tstruct xfs_rtalloc_args\targs)\nfs/xfs/libxfs/xfs_rtbitmap.c-132-{\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=150=xfs_rtbuf_get(\nfs/xfs/libxfs/xfs_rtbitmap.c:151:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-152-\txfs_fileoff_t\t\tblock,\t/* block number in bitmap or summary /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=232=xfs_rtbitmap_read_buf(\nfs/xfs/libxfs/xfs_rtbitmap.c:233:\tstruct xfs_rtalloc_args\t\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-234-\txfs_fileoff_t\t\t\tblock)\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=247=xfs_rtsummary_read_buf(\nfs/xfs/libxfs/xfs_rtbitmap.c:248:\tstruct xfs_rtalloc_args\t\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-249-\txfs_fileoff_t\t\t\tblock)\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=265=xfs_rtfind_back(\nfs/xfs/libxfs/xfs_rtbitmap.c:266:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-267-\txfs_rtxnum_t\t\tstart,\t/* starting rtext to look at /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=418=xfs_rtfind_forw(\nfs/xfs/libxfs/xfs_rtbitmap.c:419:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-420-\txfs_rtxnum_t\t\tstart,\t/* starting rtext to look at /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=568=xfs_trans_log_rtsummary(\nfs/xfs/libxfs/xfs_rtbitmap.c:569:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-570-\tunsigned int\t\tinfoword)\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=586=xfs_rtmodify_summary(\nfs/xfs/libxfs/xfs_rtbitmap.c:587:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-588-\tint\t\t\tlog,\t/ log2 of extent size /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=622=xfs_rtget_summary(\nfs/xfs/libxfs/xfs_rtbitmap.c:623:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-624-\tint\t\t\tlog,\t/* log2 of extent size /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=640=xfs_trans_log_rtbitmap(\nfs/xfs/libxfs/xfs_rtbitmap.c:641:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-642-\tunsigned int\t\tfrom,\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=659=xfs_rtmodify_range(\nfs/xfs/libxfs/xfs_rtbitmap.c:660:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-661-\txfs_rtxnum_t\t\tstart,\t/ starting rtext to modify /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=798=xfs_rtfree_range(\nfs/xfs/libxfs/xfs_rtbitmap.c:799:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-800-\txfs_rtxnum_t\t\tstart,\t/* starting rtext to free /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=871=xfs_rtcheck_range(\nfs/xfs/libxfs/xfs_rtbitmap.c:872:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-873-\txfs_rtxnum_t\t\tstart,\t/* starting rtext number of extent /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=1028=xfs_rtcheck_alloc_range(\nfs/xfs/libxfs/xfs_rtbitmap.c:1029:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.c-1030-\txfs_rtxnum_t\t\tstart,\t/* starting rtext number of extent /\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=1051=xfs_rtfree_extent(\n--\nfs/xfs/libxfs/xfs_rtbitmap.c-1058-\tstruct xfs_inode\trbmip = rtg_bitmap(rtg);\nfs/xfs/libxfs/xfs_rtbitmap.c:1059:\tstruct xfs_rtalloc_args\targs = {\nfs/xfs/libxfs/xfs_rtbitmap.c-1060-\t\t.mp\t\t= mp,\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=1154=int\nfs/xfs/libxfs/xfs_rtbitmap.c:1155:xfs_rtalloc_query_range(\nfs/xfs/libxfs/xfs_rtbitmap.c-1156-\tstruct xfs_rtgroup\t\trtg,\n--\nfs/xfs/libxfs/xfs_rtbitmap.c-1159-\txfs_rtxnum_t\t\t\tend,\nfs/xfs/libxfs/xfs_rtbitmap.c:1160:\txfs_rtalloc_query_range_fn\tfn,\nfs/xfs/libxfs/xfs_rtbitmap.c-1161-\tvoid\t\t\t\tpriv)\n--\nfs/xfs/libxfs/xfs_rtbitmap.c-1163-\tstruct xfs_mount\t\tmp = rtg_mount(rtg);\nfs/xfs/libxfs/xfs_rtbitmap.c:1164:\tstruct xfs_rtalloc_args\t\targs = {\nfs/xfs/libxfs/xfs_rtbitmap.c-1165-\t\t.rtg\t\t\t= rtg,\n--\nfs/xfs/libxfs/xfs_rtbitmap.c-1182-\twhile (start \u003c= end) {\nfs/xfs/libxfs/xfs_rtbitmap.c:1183:\t\tstruct xfs_rtalloc_rec\trec;\nfs/xfs/libxfs/xfs_rtbitmap.c-1184-\t\tint\t\t\tis_free;\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=1215=int\nfs/xfs/libxfs/xfs_rtbitmap.c:1216:xfs_rtalloc_query_all(\nfs/xfs/libxfs/xfs_rtbitmap.c-1217-\tstruct xfs_rtgroup\t\trtg,\nfs/xfs/libxfs/xfs_rtbitmap.c-1218-\tstruct xfs_trans\t\ttp,\nfs/xfs/libxfs/xfs_rtbitmap.c:1219:\txfs_rtalloc_query_range_fn\tfn,\nfs/xfs/libxfs/xfs_rtbitmap.c-1220-\tvoid\t\t\t\tpriv)\nfs/xfs/libxfs/xfs_rtbitmap.c-1221-{\nfs/xfs/libxfs/xfs_rtbitmap.c:1222:\treturn xfs_rtalloc_query_range(rtg, tp, 0, rtg-\u003ertg_extents - 1, fn,\nfs/xfs/libxfs/xfs_rtbitmap.c-1223-\t\t\tpriv);\n--\nfs/xfs/libxfs/xfs_rtbitmap.c=1227=int\nfs/xfs/libxfs/xfs_rtbitmap.c:1228:xfs_rtalloc_extent_is_free(\nfs/xfs/libxfs/xfs_rtbitmap.c-1229-\tstruct xfs_rtgroup\t\trtg,\n--\nfs/xfs/libxfs/xfs_rtbitmap.c-1234-{\nfs/xfs/libxfs/xfs_rtbitmap.c:1235:\tstruct xfs_rtalloc_args\t\targs = {\nfs/xfs/libxfs/xfs_rtbitmap.c-1236-\t\t.mp\t\t\t= rtg_mount(rtg),\n--\nfs/xfs/libxfs/xfs_rtbitmap.h-10-\nfs/xfs/libxfs/xfs_rtbitmap.h:11:struct xfs_rtalloc_args {\nfs/xfs/libxfs/xfs_rtbitmap.h-12-\tstruct xfs_rtgroup\trtg;\n--\nfs/xfs/libxfs/xfs_rtbitmap.h=220=xfs_rbmblock_wordptr(\nfs/xfs/libxfs/xfs_rtbitmap.h:221:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.h-222-\tunsigned int\t\tindex)\n--\nfs/xfs/libxfs/xfs_rtbitmap.h=238=xfs_rtbitmap_getword(\nfs/xfs/libxfs/xfs_rtbitmap.h:239:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.h-240-\tunsigned int\t\tindex)\n--\nfs/xfs/libxfs/xfs_rtbitmap.h=251=xfs_rtbitmap_setword(\nfs/xfs/libxfs/xfs_rtbitmap.h:252:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.h-253-\tunsigned int\t\tindex,\n--\nfs/xfs/libxfs/xfs_rtbitmap.h=311=xfs_rsumblock_infoptr(\nfs/xfs/libxfs/xfs_rtbitmap.h:312:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.h-313-\tunsigned int\t\tindex)\n--\nfs/xfs/libxfs/xfs_rtbitmap.h=328=xfs_suminfo_get(\nfs/xfs/libxfs/xfs_rtbitmap.h:329:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.h-330-\tunsigned int\t\tindex)\n--\nfs/xfs/libxfs/xfs_rtbitmap.h=341=xfs_suminfo_add(\nfs/xfs/libxfs/xfs_rtbitmap.h:342:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/libxfs/xfs_rtbitmap.h-343-\tunsigned int\t\tindex,\n--\nfs/xfs/libxfs/xfs_rtbitmap.h=358=xfs_rtblock_ops(\n--\nfs/xfs/libxfs/xfs_rtbitmap.h-372- /\nfs/xfs/libxfs/xfs_rtbitmap.h:373:struct xfs_rtalloc_rec {\nfs/xfs/libxfs/xfs_rtbitmap.h-374-\txfs_rtxnum_t\t\tar_startext;\n--\nfs/xfs/libxfs/xfs_rtbitmap.h-377-\nfs/xfs/libxfs/xfs_rtbitmap.h:378:typedef int (xfs_rtalloc_query_range_fn)(\nfs/xfs/libxfs/xfs_rtbitmap.h-379-\tstruct xfs_rtgroup\t\trtg,\nfs/xfs/libxfs/xfs_rtbitmap.h-380-\tstruct xfs_trans\t\ttp,\nfs/xfs/libxfs/xfs_rtbitmap.h:381:\tconst struct xfs_rtalloc_rec\trec,\nfs/xfs/libxfs/xfs_rtbitmap.h-382-\tvoid\t\t\t\tpriv);\n--\nfs/xfs/libxfs/xfs_rtbitmap.h-384-#ifdef CONFIG_XFS_RT\nfs/xfs/libxfs/xfs_rtbitmap.h:385:void xfs_rtbuf_cache_relse(struct xfs_rtalloc_args args);\nfs/xfs/libxfs/xfs_rtbitmap.h:386:int xfs_rtbitmap_read_buf(struct xfs_rtalloc_args args, xfs_fileoff_t block);\nfs/xfs/libxfs/xfs_rtbitmap.h:387:int xfs_rtsummary_read_buf(struct xfs_rtalloc_args args, xfs_fileoff_t block);\nfs/xfs/libxfs/xfs_rtbitmap.h:388:int xfs_rtcheck_range(struct xfs_rtalloc_args args, xfs_rtxnum_t start,\nfs/xfs/libxfs/xfs_rtbitmap.h-389-\t\txfs_rtxlen_t len, int val, xfs_rtxnum_t new, int stat);\nfs/xfs/libxfs/xfs_rtbitmap.h:390:int xfs_rtfind_back(struct xfs_rtalloc_args args, xfs_rtxnum_t start,\nfs/xfs/libxfs/xfs_rtbitmap.h-391-\t\txfs_rtxnum_t rtblock);\nfs/xfs/libxfs/xfs_rtbitmap.h:392:int xfs_rtfind_forw(struct xfs_rtalloc_args args, xfs_rtxnum_t start,\nfs/xfs/libxfs/xfs_rtbitmap.h-393-\t\txfs_rtxnum_t limit, xfs_rtxnum_t rtblock);\nfs/xfs/libxfs/xfs_rtbitmap.h:394:int xfs_rtmodify_range(struct xfs_rtalloc_args args, xfs_rtxnum_t start,\nfs/xfs/libxfs/xfs_rtbitmap.h-395-\t\txfs_rtxlen_t len, int val);\nfs/xfs/libxfs/xfs_rtbitmap.h:396:int xfs_rtget_summary(struct xfs_rtalloc_args args, int log,\nfs/xfs/libxfs/xfs_rtbitmap.h-397-\t\txfs_fileoff_t bbno, xfs_suminfo_t sum);\nfs/xfs/libxfs/xfs_rtbitmap.h:398:int xfs_rtmodify_summary(struct xfs_rtalloc_args args, int log,\nfs/xfs/libxfs/xfs_rtbitmap.h-399-\t\txfs_fileoff_t bbno, int delta);\nfs/xfs/libxfs/xfs_rtbitmap.h:400:int xfs_rtfree_range(struct xfs_rtalloc_args args, xfs_rtxnum_t start,\nfs/xfs/libxfs/xfs_rtbitmap.h-401-\t\txfs_rtxlen_t len);\nfs/xfs/libxfs/xfs_rtbitmap.h:402:int xfs_rtalloc_query_range(struct xfs_rtgroup rtg, struct xfs_trans tp,\nfs/xfs/libxfs/xfs_rtbitmap.h-403-\t\txfs_rtxnum_t start, xfs_rtxnum_t end,\nfs/xfs/libxfs/xfs_rtbitmap.h:404:\t\txfs_rtalloc_query_range_fn fn, void priv);\nfs/xfs/libxfs/xfs_rtbitmap.h:405:int xfs_rtalloc_query_all(struct xfs_rtgroup rtg, struct xfs_trans tp,\nfs/xfs/libxfs/xfs_rtbitmap.h:406:\t\txfs_rtalloc_query_range_fn fn, void priv);\nfs/xfs/libxfs/xfs_rtbitmap.h:407:int xfs_rtalloc_extent_is_free(struct xfs_rtgroup rtg, struct xfs_trans tp,\nfs/xfs/libxfs/xfs_rtbitmap.h-408-\t\txfs_rtxnum_t start, xfs_rtxlen_t len, bool is_free);\n--\nfs/xfs/libxfs/xfs_rtbitmap.h=433=static inline int xfs_rtfree_blocks(struct xfs_trans tp,\n--\nfs/xfs/libxfs/xfs_rtbitmap.h-438-}\nfs/xfs/libxfs/xfs_rtbitmap.h:439:# define xfs_rtalloc_query_range(m,t,l,h,f,p)\t\t(-ENOSYS)\nfs/xfs/libxfs/xfs_rtbitmap.h:440:# define xfs_rtalloc_query_all(m,t,f,p)\t\t\t(-ENOSYS)\nfs/xfs/libxfs/xfs_rtbitmap.h-441-# define xfs_rtbitmap_read_buf(a,b)\t\t\t(-ENOSYS)\n--\nfs/xfs/libxfs/xfs_rtbitmap.h-443-# define xfs_rtbuf_cache_relse(a)\t\t\t(0)\nfs/xfs/libxfs/xfs_rtbitmap.h:444:# define xfs_rtalloc_extent_is_free(m,t,s,l,i)\t\t(-ENOSYS)\nfs/xfs/libxfs/xfs_rtbitmap.h-445-static inline xfs_filblks_t\n--\nfs/xfs/libxfs/xfs_trans_resv.c=234=static unsigned int\nfs/xfs/libxfs/xfs_trans_resv.c:235:xfs_rtalloc_block_count(\nfs/xfs/libxfs/xfs_trans_resv.c-236-\tstruct xfs_mount\tmp,\n--\nfs/xfs/libxfs/xfs_trans_resv.c=357=xfs_calc_write_reservation(\n--\nfs/xfs/libxfs/xfs_trans_resv.c-373-\t\t xfs_calc_buf_res(3, mp-\u003em_sb.sb_sectsize) +\nfs/xfs/libxfs/xfs_trans_resv.c:374:\t\t xfs_calc_buf_res(xfs_rtalloc_block_count(mp, 1), blksz) +\nfs/xfs/libxfs/xfs_trans_resv.c-375-\t\t xfs_calc_buf_res(xfs_allocfree_block_count(mp, 1), blksz);\n--\nfs/xfs/libxfs/xfs_trans_resv.c=445=xfs_calc_finish_rt_efi_reservation(\n--\nfs/xfs/libxfs/xfs_trans_resv.c-452-\treturn xfs_calc_buf_res((2 * nr) + 1, mp-\u003em_sb.sb_sectsize) +\nfs/xfs/libxfs/xfs_trans_resv.c:453:\t xfs_calc_buf_res(xfs_rtalloc_block_count(mp, nr),\nfs/xfs/libxfs/xfs_trans_resv.c-454-\t\t\t mp-\u003em_sb.sb_blocksize) +\n--\nfs/xfs/scrub/bmap.c-23-#include \"xfs_health.h\"\nfs/xfs/scrub/bmap.c:24:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/bmap.c-25-#include \"xfs_rtrmap_btree.h\"\n--\nfs/xfs/scrub/bmap_repair.c-21-#include \"xfs_alloc.h\"\nfs/xfs/scrub/bmap_repair.c:22:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/bmap_repair.c-23-#include \"xfs_bmap.h\"\n--\nfs/xfs/scrub/cow_repair.c-28-#include \"xfs_refcount_btree.h\"\nfs/xfs/scrub/cow_repair.c:29:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/cow_repair.c-30-#include \"xfs_rtbitmap.h\"\n--\nfs/xfs/scrub/cow_repair.c=460=xrep_cow_alloc_rt(\n--\nfs/xfs/scrub/cow_repair.c-473-\nfs/xfs/scrub/cow_repair.c:474:\terror = xfs_rtallocate_rtgs(sc-\u003etp, NULLRTBLOCK, 1, maxrtx, 1, false,\nfs/xfs/scrub/cow_repair.c-475-\t\t\tfalse, \u0026fsbno, \u0026len);\n--\nfs/xfs/scrub/fscounters.c=390=xchk_fscount_add_frextent(\n--\nfs/xfs/scrub/fscounters.c-392-\tstruct xfs_trans\t\ttp,\nfs/xfs/scrub/fscounters.c:393:\tconst struct xfs_rtalloc_rec\trec,\nfs/xfs/scrub/fscounters.c-394-\tvoid\t\t\t\tpriv)\n--\nfs/xfs/scrub/fscounters.c=407=xchk_fscount_count_frextents(\n--\nfs/xfs/scrub/fscounters.c-427-\t\txfs_rtgroup_lock(rtg, XFS_RTGLOCK_BITMAP_SHARED);\nfs/xfs/scrub/fscounters.c:428:\t\terror = xfs_rtalloc_query_all(rtg, sc-\u003etp,\nfs/xfs/scrub/fscounters.c-429-\t\t\t\txchk_fscount_add_frextent, fsc);\n--\nfs/xfs/scrub/repair.c-42-#include \"xfs_rtgroup.h\"\nfs/xfs/scrub/repair.c:43:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/repair.c-44-#include \"xfs_metafile.h\"\n--\nfs/xfs/scrub/repair.c=1045=xrep_require_rtext_inuse(\n--\nfs/xfs/scrub/repair.c-1064-\nfs/xfs/scrub/repair.c:1065:\terror = xfs_rtalloc_extent_is_free(sc-\u003esr.rtg, sc-\u003etp, startrtx,\nfs/xfs/scrub/repair.c-1066-\t\t\tendrtx - startrtx + 1, \u0026is_free);\n--\nfs/xfs/scrub/rtbitmap.c=120=xchk_rtbitmap_rec(\n--\nfs/xfs/scrub/rtbitmap.c-122-\tstruct xfs_trans\ttp,\nfs/xfs/scrub/rtbitmap.c:123:\tconst struct xfs_rtalloc_rec rec,\nfs/xfs/scrub/rtbitmap.c-124-\tvoid\t\t\tpriv)\n--\nfs/xfs/scrub/rtbitmap.c=191=xchk_rtbitmap(\n--\nfs/xfs/scrub/rtbitmap.c-251-\trtb-\u003enext_free_rgbno = 0;\nfs/xfs/scrub/rtbitmap.c:252:\terror = xfs_rtalloc_query_all(rtg, sc-\u003etp, xchk_rtbitmap_rec, rtb);\nfs/xfs/scrub/rtbitmap.c-253-\tif (!xchk_fblock_process_error(sc, XFS_DATA_FORK, 0, \u0026error))\n--\nfs/xfs/scrub/rtbitmap.c=270=xchk_xref_is_used_rt_space(\n--\nfs/xfs/scrub/rtbitmap.c-292-\tendext = xfs_rtb_to_rtx(sc-\u003emp, rtbno + len - 1);\nfs/xfs/scrub/rtbitmap.c:293:\terror = xfs_rtalloc_extent_is_free(rtg, sc-\u003etp, startext,\nfs/xfs/scrub/rtbitmap.c-294-\t\t\tendext - startext + 1, \u0026is_free);\n--\nfs/xfs/scrub/rtbitmap.h=23=struct xchk_rtbitmap {\n--\nfs/xfs/scrub/rtbitmap.h-35-\t/* stuff for staging a new bitmap /\nfs/xfs/scrub/rtbitmap.h:36:\tstruct xfs_rtalloc_args\targs;\nfs/xfs/scrub/rtbitmap.h-37-\tstruct xrep_tempexch\ttempexch;\n--\nfs/xfs/scrub/rtbitmap_repair.c-14-#include \"xfs_trans.h\"\nfs/xfs/scrub/rtbitmap_repair.c:15:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/rtbitmap_repair.c-16-#include \"xfs_inode.h\"\n--\nfs/xfs/scrub/rtrefcount.c-21-#include \"xfs_rtrefcount_btree.h\"\nfs/xfs/scrub/rtrefcount.c:22:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/rtrefcount.c-23-#include \"xfs_ag.h\"\n--\nfs/xfs/scrub/rtrefcount_repair.c-29-#include \"xfs_quota.h\"\nfs/xfs/scrub/rtrefcount_repair.c:30:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/rtrefcount_repair.c-31-#include \"xfs_ag.h\"\n--\nfs/xfs/scrub/rtrmap.c-21-#include \"xfs_inode.h\"\nfs/xfs/scrub/rtrmap.c:22:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/rtrmap.c-23-#include \"xfs_rtgroup.h\"\n--\nfs/xfs/scrub/rtrmap_repair.c-29-#include \"xfs_quota.h\"\nfs/xfs/scrub/rtrmap_repair.c:30:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/rtrmap_repair.c-31-#include \"xfs_ag.h\"\n--\nfs/xfs/scrub/rtsummary.c=163=xchk_rtsum_record_free(\n--\nfs/xfs/scrub/rtsummary.c-165-\tstruct xfs_trans\t\ttp,\nfs/xfs/scrub/rtsummary.c:166:\tconst struct xfs_rtalloc_rec\trec,\nfs/xfs/scrub/rtsummary.c-167-\tvoid\t\t\t\tpriv)\n--\nfs/xfs/scrub/rtsummary.c=210=xchk_rtsum_compute(\n--\nfs/xfs/scrub/rtsummary.c-220-\nfs/xfs/scrub/rtsummary.c:221:\treturn xfs_rtalloc_query_all(rtg, sc-\u003etp, xchk_rtsum_record_free, sc);\nfs/xfs/scrub/rtsummary.c-222-}\n--\nfs/xfs/scrub/rtsummary.h=9=struct xchk_rtsummary {\n--\nfs/xfs/scrub/rtsummary.h-12-#endif\nfs/xfs/scrub/rtsummary.h:13:\tstruct xfs_rtalloc_args\targs;\nfs/xfs/scrub/rtsummary.h-14-\n--\nfs/xfs/scrub/rtsummary_repair.c-14-#include \"xfs_trans.h\"\nfs/xfs/scrub/rtsummary_repair.c:15:#include \"xfs_rtalloc.h\"\nfs/xfs/scrub/rtsummary_repair.c-16-#include \"xfs_inode.h\"\n--\nfs/xfs/xfs_bmap_util.c-22-#include \"xfs_bmap_btree.h\"\nfs/xfs/xfs_bmap_util.c:23:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_bmap_util.c-24-#include \"xfs_error.h\"\n--\nfs/xfs/xfs_discard.c=511=xfs_trim_gather_rtextent(\n--\nfs/xfs/xfs_discard.c-513-\tstruct xfs_trans\t\ttp,\nfs/xfs/xfs_discard.c:514:\tconst struct xfs_rtalloc_rec\trec,\nfs/xfs/xfs_discard.c-515-\tvoid\t\t\t\tpriv)\n--\nfs/xfs/xfs_discard.c=555=xfs_trim_rtextents(\n--\nfs/xfs/xfs_discard.c-577-\t\txfs_rtgroup_lock(rtg, XFS_RTGLOCK_BITMAP_SHARED);\nfs/xfs/xfs_discard.c:578:\t\terror = xfs_rtalloc_query_range(rtg, tp, low, high,\nfs/xfs/xfs_discard.c-579-\t\t\t\txfs_trim_gather_rtextent, \u0026tr);\n--\nfs/xfs/xfs_discard.c=624=xfs_trim_gather_rtgroup_extent(\n--\nfs/xfs/xfs_discard.c-626-\tstruct xfs_trans\t\ttp,\nfs/xfs/xfs_discard.c:627:\tconst struct xfs_rtalloc_rec\trec,\nfs/xfs/xfs_discard.c-628-\tvoid\t\t\t\tpriv)\n--\nfs/xfs/xfs_discard.c=672=xfs_trim_rtgroup_extents(\n--\nfs/xfs/xfs_discard.c-703-\t\txfs_rtgroup_lock(rtg, XFS_RTGLOCK_BITMAP_SHARED);\nfs/xfs/xfs_discard.c:704:\t\terror = xfs_rtalloc_query_range(rtg, tp, low, high,\nfs/xfs/xfs_discard.c-705-\t\t\t\txfs_trim_gather_rtgroup_extent, \u0026tr);\n--\nfs/xfs/xfs_extfree_item.c-27-#include \"xfs_log_recover.h\"\nfs/xfs/xfs_extfree_item.c:28:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_extfree_item.c-29-#include \"xfs_inode.h\"\n--\nfs/xfs/xfs_fsmap.c=716=xfs_getfsmap_rtdev_rtbitmap_helper(\n--\nfs/xfs/xfs_fsmap.c-718-\tstruct xfs_trans\t\ttp,\nfs/xfs/xfs_fsmap.c:719:\tconst struct xfs_rtalloc_rec\trec,\nfs/xfs/xfs_fsmap.c-720-\tvoid\t\t\t\tpriv)\n--\nfs/xfs/xfs_fsmap.c=752=xfs_getfsmap_rtdev_rtbitmap(\n--\nfs/xfs/xfs_fsmap.c-796-\t\txfs_rtgroup_lock(rtg, XFS_RTGLOCK_BITMAP_SHARED);\nfs/xfs/xfs_fsmap.c:797:\t\terror = xfs_rtalloc_query_range(rtg, tp, start_rtx, end_rtx,\nfs/xfs/xfs_fsmap.c-798-\t\t\t\txfs_getfsmap_rtdev_rtbitmap_helper, info);\n--\nfs/xfs/xfs_fsmap.c-807-\t\tif (rtg_rgno(rtg) == end_rgno) {\nfs/xfs/xfs_fsmap.c:808:\t\t\tstruct xfs_rtalloc_rec\tahigh = {\nfs/xfs/xfs_fsmap.c-809-\t\t\t\t.ar_startext\t= min(end_rtx + 1,\n--\nfs/xfs/xfs_fsops.c-23-#include \"xfs_trace.h\"\nfs/xfs/xfs_fsops.c:24:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_fsops.c-25-#include \"xfs_rtrmap_btree.h\"\n--\nfs/xfs/xfs_ioctl.c-13-#include \"xfs_inode.h\"\nfs/xfs/xfs_ioctl.c:14:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_ioctl.c-15-#include \"xfs_iwalk.h\"\n--\nfs/xfs/xfs_ioctl32.c-18-#include \"xfs_fsops.h\"\nfs/xfs/xfs_ioctl32.c:19:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_ioctl32.c-20-#include \"xfs_da_format.h\"\n--\nfs/xfs/xfs_mount.c-18-#include \"xfs_alloc.h\"\nfs/xfs/xfs_mount.c:19:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_mount.c-20-#include \"xfs_bmap.h\"\n--\nfs/xfs/xfs_mount.c=500=xfs_check_summary_counts(\n--\nfs/xfs/xfs_mount.c-562-\tif (xfs_has_realtime(mp) \u0026\u0026 !xfs_has_zoned(mp) \u0026\u0026 !xfs_is_clean(mp)) {\nfs/xfs/xfs_mount.c:563:\t\terror = xfs_rtalloc_reinit_frextents(mp);\nfs/xfs/xfs_mount.c-564-\t\tif (error)\n--\nfs/xfs/xfs_notify_failure.c-18-#include \"xfs_rmap_btree.h\"\nfs/xfs/xfs_notify_failure.c:19:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_notify_failure.c-20-#include \"xfs_trans.h\"\n--\nfs/xfs/xfs_reflink.c-33-#include \"xfs_rtrefcount_btree.h\"\nfs/xfs/xfs_reflink.c:34:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_reflink.c-35-#include \"xfs_rtgroup.h\"\n--\nfs/xfs/xfs_rtalloc.c-21-#include \"xfs_icache.h\"\nfs/xfs/xfs_rtalloc.c:22:#include \"xfs_rtalloc.h\"\nfs/xfs/xfs_rtalloc.c-23-#include \"xfs_sb.h\"\n--\nfs/xfs/xfs_rtalloc.c=43=xfs_rtany_summary(\nfs/xfs/xfs_rtalloc.c:44:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/xfs_rtalloc.c-45-\tint\t\t\tlow,\t/* low log2 extent size /\n--\nfs/xfs/xfs_rtalloc.c=99=xfs_rtcopy_summary(\nfs/xfs/xfs_rtalloc.c:100:\tstruct xfs_rtalloc_args\toargs,\nfs/xfs/xfs_rtalloc.c:101:\tstruct xfs_rtalloc_args\tnargs)\nfs/xfs/xfs_rtalloc.c-102-{\n--\nfs/xfs/xfs_rtalloc.c=138=STATIC int\nfs/xfs/xfs_rtalloc.c:139:xfs_rtallocate_range(\nfs/xfs/xfs_rtalloc.c:140:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/xfs_rtalloc.c-141-\txfs_rtxnum_t\t\tstart,\t/* start rtext to allocate /\n--\nfs/xfs/xfs_rtalloc.c=209=static inline xfs_rtxlen_t\nfs/xfs/xfs_rtalloc.c:210:xfs_rtalloc_align_len(\nfs/xfs/xfs_rtalloc.c-211-\txfs_rtxlen_t\trtxlen,\n--\nfs/xfs/xfs_rtalloc.c=223=static inline xfs_rtxlen_t\nfs/xfs/xfs_rtalloc.c:224:xfs_rtallocate_clamp_len(\nfs/xfs/xfs_rtalloc.c-225-\tstruct xfs_rtgroup\trtg,\n--\nfs/xfs/xfs_rtalloc.c-232-\tret = min(rtg-\u003ertg_extents, startrtx + rtxlen) - startrtx;\nfs/xfs/xfs_rtalloc.c:233:\treturn xfs_rtalloc_align_len(ret, prod);\nfs/xfs/xfs_rtalloc.c-234-}\n--\nfs/xfs/xfs_rtalloc.c=242=STATIC int\nfs/xfs/xfs_rtalloc.c:243:xfs_rtallocate_extent_block(\nfs/xfs/xfs_rtalloc.c:244:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/xfs_rtalloc.c-245-\txfs_fileoff_t\t\tbbno,\t/ bitmap block number /\n--\nfs/xfs/xfs_rtalloc.c-270-\t\t/ Make sure we don't scan off the end of the rt volume. /\nfs/xfs/xfs_rtalloc.c:271:\t\tscanlen = xfs_rtallocate_clamp_len(args-\u003ertg, i, maxlen, prod);\nfs/xfs/xfs_rtalloc.c-272-\t\tif (scanlen \u003c minlen)\n--\nfs/xfs/xfs_rtalloc.c-323-\t /\nfs/xfs/xfs_rtalloc.c:324:\tbestlen = xfs_rtalloc_align_len(bestlen, prod);\nfs/xfs/xfs_rtalloc.c-325-\tif (bestlen \u003c minlen)\n--\nfs/xfs/xfs_rtalloc.c=346=STATIC int\nfs/xfs/xfs_rtalloc.c:347:xfs_rtallocate_extent_exact(\nfs/xfs/xfs_rtalloc.c:348:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/xfs_rtalloc.c-349-\txfs_rtxnum_t\t\tstart,\t/ starting rtext number to allocate /\n--\nfs/xfs/xfs_rtalloc.c-365-\t/ Make sure we don't run off the end of the rt volume. /\nfs/xfs/xfs_rtalloc.c:366:\tscanlen = xfs_rtallocate_clamp_len(args-\u003ertg, start, maxlen, prod);\nfs/xfs/xfs_rtalloc.c-367-\tif (scanlen \u003c minlen)\n--\nfs/xfs/xfs_rtalloc.c-389-\t/ Ensure alloclen is a multiple of prod. /\nfs/xfs/xfs_rtalloc.c:390:\talloclen = xfs_rtalloc_align_len(alloclen, prod);\nfs/xfs/xfs_rtalloc.c-391-\tif (alloclen \u003c minlen)\n--\nfs/xfs/xfs_rtalloc.c=404=STATIC int\nfs/xfs/xfs_rtalloc.c:405:xfs_rtallocate_extent_near(\nfs/xfs/xfs_rtalloc.c:406:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/xfs_rtalloc.c-407-\txfs_rtxnum_t\t\tstart,\t/* starting rtext number to allocate /\n--\nfs/xfs/xfs_rtalloc.c-434-\t /\nfs/xfs/xfs_rtalloc.c:435:\terror = xfs_rtallocate_extent_exact(args, start, minlen, maxlen, len,\nfs/xfs/xfs_rtalloc.c-436-\t\t\tprod, rtx);\n--\nfs/xfs/xfs_rtalloc.c-473-\t\t\t\t /\nfs/xfs/xfs_rtalloc.c:474:\t\t\t\terror = xfs_rtallocate_extent_block(args,\nfs/xfs/xfs_rtalloc.c-475-\t\t\t\t\t\tbbno + i, minlen, maxavail, len,\n--\nfs/xfs/xfs_rtalloc.c-508-\t\t\t\tfor (; j \u003e= i; j--) {\nfs/xfs/xfs_rtalloc.c:509:\t\t\t\t\terror = xfs_rtallocate_extent_block(args,\nfs/xfs/xfs_rtalloc.c-510-\t\t\t\t\t\t\tbbno + j, minlen,\n--\nfs/xfs/xfs_rtalloc.c=551=static int\nfs/xfs/xfs_rtalloc.c:552:xfs_rtalloc_sumlevel(\nfs/xfs/xfs_rtalloc.c:553:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/xfs_rtalloc.c-554-\tint\t\t\tl,\t/* level number /\n--\nfs/xfs/xfs_rtalloc.c-580-\t\t /\nfs/xfs/xfs_rtalloc.c:581:\t\terror = xfs_rtallocate_extent_block(args, i, minlen, maxlen,\nfs/xfs/xfs_rtalloc.c-582-\t\t\t\tlen, \u0026n, prod, rtx);\n--\nfs/xfs/xfs_rtalloc.c=602=static int\nfs/xfs/xfs_rtalloc.c:603:xfs_rtallocate_extent_size(\nfs/xfs/xfs_rtalloc.c:604:\tstruct xfs_rtalloc_args\targs,\nfs/xfs/xfs_rtalloc.c-605-\txfs_rtxlen_t\t\tminlen,\t/ minimum length to allocate /\n--\nfs/xfs/xfs_rtalloc.c-627-\tfor (l = xfs_highbit32(maxlen); l \u003c args-\u003emp-\u003em_rsumlevels; l++) {\nfs/xfs/xfs_rtalloc.c:628:\t\terror = xfs_rtalloc_sumlevel(args, l, minlen, maxlen, prod, len,\nfs/xfs/xfs_rtalloc.c-629-\t\t\t\trtx);\n--\nfs/xfs/xfs_rtalloc.c-650-\tfor (l = xfs_highbit32(maxlen); l \u003e= xfs_highbit32(minlen); l--) {\nfs/xfs/xfs_rtalloc.c:651:\t\terror = xfs_rtalloc_sumlevel(args, l,\nfs/xfs/xfs_rtalloc.c-652-\t\t\t\tmax_t(xfs_rtxlen_t, minlen, 1 \u003c\u003c l),\n--\nfs/xfs/xfs_rtalloc.c=777=xfs_growfs_rt_free_new(\nfs/xfs/xfs_rtalloc.c-778-\tstruct xfs_rtgroup\trtg,\nfs/xfs/xfs_rtalloc.c:779:\tstruct xfs_rtalloc_args\tnargs,\nfs/xfs/xfs_rtalloc.c-780-\txfs_rtbxlen_t\t\tfreed_rtx)\n--\nfs/xfs/xfs_rtalloc.c=826=xfs_growfs_rt_init_rtsb(\nfs/xfs/xfs_rtalloc.c:827:\tconst struct xfs_rtalloc_args\tnargs,\nfs/xfs/xfs_rtalloc.c-828-\tconst struct xfs_rtgroup\trtg,\nfs/xfs/xfs_rtalloc.c:829:\tconst struct xfs_rtalloc_args\targs)\nfs/xfs/xfs_rtalloc.c-830-{\n--\nfs/xfs/xfs_rtalloc.c=951=xfs_growfs_rt_bmblock(\n--\nfs/xfs/xfs_rtalloc.c-959-\tstruct xfs_inode\trsumip = rtg_summary(rtg);\nfs/xfs/xfs_rtalloc.c:960:\tstruct xfs_rtalloc_args\targs = {\nfs/xfs/xfs_rtalloc.c-961-\t\t.mp\t\t= mp,\n--\n\n" }
11/2	2026/09/23 06:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 31919 output: 45 thoughts: 1150 Thoughts: Analyzing Write Streams Feature in XFS Okay, let's break this down. My initial focus is on the configurations related to this write stream functionality. I see `CONFIG_XFS_FS` and `CONFIG_XFS_RT` as relevant. I quickly confirm that `XFS_RT` depends on `XFS_FS`, which makes sense. I also note that `FS_IOMAP` is selected by `XFS_FS` and `fs/write_streams.c` is always compiled. Now, I need to understand which functions are modified and how they relate to the "FocusSymbols guidelines." I need to identify the feature-specific entry points, avoiding ubiquitous functions like generic allocators. I've reviewed the diff and have identified the modified symbols. I have considered each of these symbols within the relevant source files: `fs/write_streams.c`, `fs/fcntl.c`, `fs/xfs/libxfs/xfs_bmap.c`, `fs/xfs/xfs_buf.c`, `fs/xfs/xfs_inode.c`, `fs/xfs/xfs_ioctl.c`, `fs/xfs/xfs_rtalloc.c`, and `fs/iomap/direct-io.c` and `fs/iomap/ioend.c`. Specifically, in `fs/write_streams.c`, I'm looking at `write_stream_release` (despite being static, I'll need to check if it's targeted) as well as the more obvious ones: `write_stream_pool_init`, `write_stream_pool_destroy`, `write_stream_alloc_fd`, and `write_stream_get_id`. I have also reviewed the `fs/xfs/xfs_inode.c` where I have found `xfs_inode_max_write_streams`, `xfs_inode_set_write_stream`, `xfs_inode_clear_write_stream`. Then the `fs/xfs/xfs_buf.c` file where I have found `xfs_buftarg_init_streams`. Lastly, I need to check `xfs_bmap_btalloc` in `fs/xfs/libxfs/xfs_bmap.c`. I have a note here to verify that this function is non-static as I believe it to be a key entry point. I'll need to double check the source file.
12/2	2026/09/23 06:45	tool	grepper	0m Args: { "Expression": "^xfs_bmap_btalloc", "PathPrefix": "fs/xfs/libxfs/xfs_bmap.c" } Results: { "Output": "fs/xfs/libxfs/xfs_bmap.c=3195=static int\nfs/xfs/libxfs/xfs_bmap.c:3196:xfs_bmap_btalloc_select_lengths(\nfs/xfs/libxfs/xfs_bmap.c-3197-\tstruct xfs_bmalloca\tap,\n--\nfs/xfs/libxfs/xfs_bmap.c=3406=static int\nfs/xfs/libxfs/xfs_bmap.c:3407:xfs_bmap_btalloc_at_eof(\nfs/xfs/libxfs/xfs_bmap.c-3408-\tstruct xfs_bmalloca\tap,\n--\nfs/xfs/libxfs/xfs_bmap.c=3509=int\nfs/xfs/libxfs/xfs_bmap.c:3510:xfs_bmap_btalloc_low_space(\nfs/xfs/libxfs/xfs_bmap.c-3511-\tstruct xfs_bmalloca\tap,\n--\nfs/xfs/libxfs/xfs_bmap.c=3532=static int\nfs/xfs/libxfs/xfs_bmap.c:3533:xfs_bmap_btalloc_filestreams(\nfs/xfs/libxfs/xfs_bmap.c-3534-\tstruct xfs_bmalloca\tap,\n--\nfs/xfs/libxfs/xfs_bmap.c=3605=static int\nfs/xfs/libxfs/xfs_bmap.c:3606:xfs_bmap_btalloc_from_blkno(\nfs/xfs/libxfs/xfs_bmap.c-3607-\tstruct xfs_bmalloca\tap,\n--\nfs/xfs/libxfs/xfs_bmap.c=3647=static int\nfs/xfs/libxfs/xfs_bmap.c:3648:xfs_bmap_btalloc_write_stream(\nfs/xfs/libxfs/xfs_bmap.c-3649-\tstruct xfs_bmalloca\tap,\n--\nfs/xfs/libxfs/xfs_bmap.c=3662=static int\nfs/xfs/libxfs/xfs_bmap.c:3663:xfs_bmap_btalloc_best_length(\nfs/xfs/libxfs/xfs_bmap.c-3664-\tstruct xfs_bmalloca\tap,\n--\nfs/xfs/libxfs/xfs_bmap.c=3672=static int\nfs/xfs/libxfs/xfs_bmap.c:3673:xfs_bmap_btalloc(\nfs/xfs/libxfs/xfs_bmap.c-3674-\tstruct xfs_bmalloca\tap)\n" }
13/2	2026/09/23 06:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34448 output: 45 thoughts: 31 Thoughts: Okay, here's my take on those thoughts, tailored for an expert audience, presented in the first person: Analyzing the Allocation Strategy in XFS Alright, so `xfs_bmap_btalloc` is declared as `static`. That immediately piques my interest. As a highly experienced XFS developer, I understand the implications of `static` functions – they're only visible within the current compilation unit. My immediate thought is, what are the use cases? Where within the XFS codebase is `xfs_bmap_btalloc` being called? It's time to trace the call paths. I need to understand the allocation strategy that's being employed. I need to know where and how this routine is leveraged, specifically looking for performance critical regions. Let's delve into the call graph and see who's invoking this particular function.
14/2	2026/09/23 06:45	tool	grepper	0m Args: { "Expression": "xfs_bmap_btalloc\\(", "PathPrefix": "fs/xfs/libxfs/xfs_bmap.c" } Results: { "Output": "fs/xfs/libxfs/xfs_bmap.c=3672=static int\nfs/xfs/libxfs/xfs_bmap.c:3673:xfs_bmap_btalloc(\nfs/xfs/libxfs/xfs_bmap.c-3674-\tstruct xfs_bmalloca\t*ap)\n--\nfs/xfs/libxfs/xfs_bmap.c=3949=xfs_bmapi_allocate(\n--\nfs/xfs/libxfs/xfs_bmap.c-3989-\telse\nfs/xfs/libxfs/xfs_bmap.c:3990:\t\terror = xfs_bmap_btalloc(bma);\nfs/xfs/libxfs/xfs_bmap.c-3991-\tif (error)\n" }
15/2	2026/09/23 06:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 34935 output: 41 thoughts: 80 Thoughts: Here's my thought process, as it relates to the kernel code: Diving into the XFS Real-time Allocation Path Okay, so I see that `xfs_bmapi_allocate` is the function that's calling things, which makes sense; that's the core allocation entry point. But what's really interesting is where it's going – and that's where `fs/xfs/xfs_rtalloc.c` comes into play. I know the XFS real-time allocation system intimately, so I suspect this is going to be the central point of the real-time allocator. Specifically, I see `xfs_bmap_rtalloc` there. Hmm, and it's not static, so it's likely called from other places besides the file. That’s an important point for cross-file debugging. Now, let’s drill down into `xfs_bmap_rtalloc` and see how the real-time allocation mechanics are actually implemented. Let's see what’s going on inside.
16/2	2026/09/23 06:45	tool	grepper	0m Args: { "Expression": "^xfs_bmap_rtalloc", "PathPrefix": "fs/xfs/xfs_rtalloc.c" } Results: { "Output": "fs/xfs/xfs_rtalloc.c=2185=int\nfs/xfs/xfs_rtalloc.c:2186:xfs_bmap_rtalloc(\nfs/xfs/xfs_rtalloc.c-2187-\tstruct xfs_bmalloca\t*ap)\n" }
17/2	2026/09/23 06:45	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 35378 output: 22 thoughts: 1700 Thoughts: Analyzing Write Stream Implementation for Focus Symbols Okay, so I've got this new write stream functionality for XFS to analyze. First, yes! I've identified several key functions involved. Let's start with those in `fs/xfs/xfs_ioctl.c`: `xfs_ioc_write_stream_get_max`, `xfs_ioc_write_stream_alloc`, and `xfs_ioc_write_stream_set`. The interesting thing is that they are `static` within that file, and called by `xfs_file_ioctl`. These _could_ be inlined, so I need to make sure I identify non-static callers as well. And I do: I see that `xfs_inode_set_write_stream`, `xfs_inode_max_write_streams`, and `xfs_inode_clear_write_stream` in `xfs_inode.c` specifically use those! Excellent. I also see that `write_stream_alloc_fd`, `write_stream_get_id`, `write_stream_pool_init`, and `write_stream_pool_destroy` in `write_streams.c` are EXPORT_SYMBOL_GPL and non-static. Those are definitely symbols. `fcntl_set_rw_hint` in `fs/fcntl.c` is static, but is used by `do_fcntl`. I noted `xfs_buftarg_init_streams`, which is non-static in `fs/xfs/xfs_buf.c`, and `xfs_bmap_rtalloc` is non-static in `fs/xfs/xfs_rtalloc.c`. The `xfs_ioc_write_stream_` ioctl handlers might be inlined, but I need to make sure I am accounting for the cases where they are not. Those static `xfs_ioc_write_stream_` functions in `xfs_ioctl.c`, being 13-28 lines long, are probably not inlined. The non-static functions will definitely not be inlined across translation units! And the `xfs_bmapi_allocate` and `xfs_bmap_rtalloc` functions are also important allocation functions. I don't need to track `iomap_dio_bio_iter_one` or `iomap_alloc_ioend` as those simply set the write stream. So, the core of the new logic seems to be around write stream file descriptor management and the XFS write stream support. Now, let's remember the instructions for FocusSymbols. I need to list functions that implement the specific logic or are API entrypoints. Also, the instructions are careful about static inline functions, and that is a major concern here. The goal is to avoid those ubiquitous wrappers and focus on the specific changes. So what's the core logic? I've got: * `write_stream_alloc_fd` * `write_stream_get_id` * `write_stream_pool_init` * `write_stream_pool_destroy` * `write_stream_release` * `xfs_ioc_write_stream_alloc` * `xfs_ioc_write_stream_set` * `xfs_ioc_write_stream_get_max` * `xfs_inode_set_write_stream` * `xfs_inode_clear_write_stream` * `xfs_inode_max_write_streams` * `xfs_buftarg_init_streams` * `xfs_bmap_rtalloc` * `xfs_bmap_btalloc` / `xfs_bmap_btalloc_write_stream` * `fcntl_set_rw_hint` I can track static functions in .c files if they are in kallsyms or symbol coverage! And including both the entry points and implementation functions is a good idea. That means: * `write_stream_alloc_fd` * `write_stream_get_id` * `write_stream_pool_init` * `write_stream_pool_destroy` * `write_stream_release` * `xfs_ioc_write_stream_alloc` * `xfs_ioc_write_stream_set` * `xfs_ioc_write_stream_get_max` * `xfs_inode_set_write_stream` * `xfs_inode_
18/2	2026/09/23 06:46	tool	grepper	0m Args: { "Expression": "bdev_max_write_streams" } Results: { "Output": "block/fops.c=394=static ssize_t blkdev_direct_IO(struct kiocb iocb, struct iov_iter iter)\n--\nblock/fops.c-405-\tif (iov_iter_rw(iter) == WRITE) {\nblock/fops.c:406:\t\tu16 max_write_streams = bdev_max_write_streams(bdev);\nblock/fops.c-407-\n--\nfs/f2fs/file.c=5464=static bool f2fs_valid_write_stream(struct f2fs_sb_info sbi, u8 write_stream)\n--\nfs/f2fs/file.c-5470-\tif (!f2fs_is_multi_device(sbi))\nfs/f2fs/file.c:5471:\t\treturn write_stream \u003c= bdev_max_write_streams(sbi-\u003esb-\u003es_bdev);\nfs/f2fs/file.c-5472-\nfs/f2fs/file.c-5473-\tfor (i = 0; i \u003c sbi-\u003es_ndevs; i++)\nfs/f2fs/file.c:5474:\t\tif (write_stream \u003e bdev_max_write_streams(FDEV(i).bdev))\nfs/f2fs/file.c-5475-\t\t\treturn false;\n--\nfs/f2fs/segment.c=3742=u8 f2fs_io_type_to_write_stream(struct block_device bdev,\n--\nfs/f2fs/segment.c-3744-{\nfs/f2fs/segment.c:3745:\tunsigned short nr = bdev_max_write_streams(bdev);\nfs/f2fs/segment.c-3746-\n--\nfs/xfs/xfs_buf.c=1707=xfs_buftarg_init_streams(\n--\nfs/xfs/xfs_buf.c-1713-\nfs/xfs/xfs_buf.c:1714:\thw_streams = bdev_max_write_streams(btp-\u003ebt_bdev);\nfs/xfs/xfs_buf.c-1715-\tif (hw_streams)\n--\ninclude/linux/blkdev.h=1298=static inline unsigned int bdev_max_segments(struct block_device bdev)\n--\ninclude/linux/blkdev.h-1302-\ninclude/linux/blkdev.h:1303:static inline unsigned short bdev_max_write_streams(struct block_device bdev)\ninclude/linux/blkdev.h-1304-{\n" }
19/2	2026/09/23 06:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 38817 output: 37 thoughts: 48 Thoughts: Okay, here's my summary, tailored for an expert audience, in the first person: Diving into Block Device Write Stream Limits Right, so I need to understand how the system manages concurrent write streams to block devices. My starting point is that `bdev_max_write_streams` is the likely key. Let's see... I'll jump straight into the kernel source, specifically `include/linux/blkdev.h`. I'm going to quickly check the definition of `bdev_max_write_streams` there. I want to see how it's declared, the data type used, and any associated comments or related macros. I'm especially interested in whether it's a hard limit, a tunable parameter, or potentially something that’s dynamically calculated based on other system parameters. Understanding the fundamental definition is crucial before I start poking around the code that uses this value. Let's see what we find.
20/2	2026/09/23 06:46	tool	read-file	0m Args: { "File": "include/linux/blkdev.h", "FirstLine": 1300, "LineCount": 20 } Results: { "Contents": "1300:\t\treturn queue_max_segments(bdev_get_queue(bdev));\n1301:\t}\n1302:\t\n1303:\tstatic inline unsigned short bdev_max_write_streams(struct block_device bdev)\n1304:\t{\n1305:\t\tif (bdev_is_partition(bdev))\n1306:\t\t\treturn 0;\n1307:\t\treturn bdev_limits(bdev)-\u003emax_write_streams;\n1308:\t}\n1309:\t\n1310:\tstatic inline unsigned queue_logical_block_size(const struct request_queue q)\n1311:\t{\n1312:\t\treturn q-\u003elimits.logical_block_size;\n1313:\t}\n1314:\t\n1315:\tstatic inline unsigned int bdev_logical_block_size(struct block_device *bdev)\n1316:\t{\n1317:\t\treturn queue_logical_block_size(bdev_get_queue(bdev));\n1318:\t}\n1319:\t\n" }
21/2	2026/09/23 06:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 39400 output: 20 thoughts: 196 Thoughts: Investigating Write Stream Configuration Okay, so I don't think there's anything special I need to do regarding `bdev_max_write_streams`, that seems pretty straightforward. Let's dig deeper and see if there are any other configurations related to `write_streams.c`. I need to figure out how it's integrated. Looking at the `fs/Makefile`, it appears to be directly built into the kernel core, alongside `anon_inodes.o`. Hmm, it's just `obj-y += anon_inodes.o write_streams.o`, right in the core file system stuff. Interesting. Alright, so `XFS_FS` builds `fs/xfs` generally, and `XFS_RT` brings in `xfs_rtalloc.o` and related realtime support. Let's make sure I'm not missing anything. I need to scan the diff again to make sure there aren't any other related configs lurking in other files. Okay, I see that `fs/iomap/direct-io.c` and `fs/iomap/ioend.c` use `CONFIG_FS_IOMAP`, which is selected by `CONFIG_XFS_FS`. That makes sense in the context of XFS. Now, just to be absolutely certain, I should verify the definition of `FS_IOMAP`. I should be able to find it in `fs/iomap/Kconfig` or possibly even the top-level `fs/Kconfig`. I'll confirm that definition.
22/2	2026/09/23 06:46	tool	grepper	0m Args: { "Expression": "config FS_IOMAP" } Results: { "Output": "fs/Kconfig=12=config VALIDATE_FS_PARSER\n--\nfs/Kconfig-17-\nfs/Kconfig:18:config FS_IOMAP\nfs/Kconfig-19-\tbool\n" }
23/2	2026/09/23 06:46	llm	patch-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 40017 output: 361 thoughts: 544 Thoughts: My Assessment of the XFS Write Stream Fuzzing Target Okay, let's break this down systematically. My initial assessment is that the code under review, related to XFS write streams, is indeed a viable target for fuzzing. We have `FS_IOMAP` selected by `XFS_FS` and `XFS_RT` depending on `XFS_FS`. Thus, enabling the right configurations for fuzzing involves enabling both `XFS_FS` and `XFS_RT`. These are the key configurations required to expose the relevant code. Now, let's confirm the "WorthFuzzing" status. We need a sanity check, right? Looking at the code, it's clear this touches critical areas: the core filesystems, the VFS, and specifically XFS. Specifically, the identified code touches the following: * The generic write stream fd infrastructure (`fs/write_streams.c`). * New `ioctls` like `FS_IOC_WRITE_STREAM_GET_MAX`, `FS_IOC_WRITE_STREAM_ALLOC`, `FS_IOC_WRITE_STREAM_SET` on XFS files. * It interacts with `fcntl`'s `rw` hints (`F_SET_RW_HINT`), inode locking, and file lifetime hints. * Crucially, there are block allocation modifications within XFS, including allocation within Allocation Groups (AG) and Real-time (RT) areas, specifically with stream IDs. * The code involves `iomap` direct I/O and buffered writeback bio submission and merging (`iomap_dio_bio_iter_one`, `iomap_alloc_ioend`, `iomap_can_add_to_ioend`). This all strongly suggests we have a substantial surface area. The second check is whether this can actually be tested, and the answer is yes. This is all reachable in standard virtualized environments, such as QEMU/KVM, using XFS filesystem images or loopback devices. This is crucial for practical fuzzing. Therefore, my conclusion: WorthFuzzing = true. Now, it is essential that we properly document what we are doing. We need to clearly outline the FocusSymbols: This is a critical step to make sure we stay focused. We have these symbols to test: `write_stream_alloc_fd`, `write_stream_get_id`, `write_stream_pool_init`, `write_stream_pool_destroy`, `write_stream_release`, `xfs_ioc_write_stream_alloc`, `xfs_ioc_write_stream_set`, `xfs_ioc_write_stream_get_max`, `xfs_inode_set_write_stream`, `xfs_inode_clear_write_stream`, `xfs_inode_max_write_streams`, `xfs_buftarg_init_streams`, `xfs_bmap_btalloc_write_stream`, `xfs_bmap_write_stream_agno`, `xfs_bmap_write_stream_rtbno`, and `fcntl_set_rw_hint`. And, to be clear, the required EnableConfigs are: `XFS_FS` and `XFS_RT`. Alright, I believe the assessment is complete. Let's call `set-results`.
24/2	2026/09/23 06:46	tool	set-results	0m Args: { "EnableConfigs": [ "XFS_FS", "XFS_RT" ], "FocusSymbols": [ "write_stream_alloc_fd", "write_stream_get_id", "write_stream_pool_init", "write_stream_pool_destroy", "write_stream_release", "xfs_ioc_write_stream_alloc", "xfs_ioc_write_stream_set", "xfs_ioc_write_stream_get_max", "xfs_inode_set_write_stream", "xfs_inode_clear_write_stream", "xfs_inode_max_write_streams", "xfs_buftarg_init_streams", "xfs_bmap_btalloc_write_stream", "xfs_bmap_write_stream_agno", "xfs_bmap_write_stream_rtbno", "fcntl_set_rw_hint" ], "Reasoning": "The patch series introduces generic write-stream fd management and integrates write stream allocation and hints into XFS and iomap. It adds new ioctls (FS_IOC_WRITE_STREAM_GET_MAX, FS_IOC_WRITE_STREAM_ALLOC, FS_IOC_WRITE_STREAM_SET), modifies fcntl write hint semantics, introduces anon-inode write-stream fds, and changes AG and realtime block allocation logic in XFS. All changes execute in core VFS/XFS code and are directly reachable from unprivileged/privileged userspace in standard virtualized environments.", "WorthFuzzing": true } Results: { "EnableConfigs": [ "XFS_FS", "XFS_RT" ], "FocusSymbols": [ "write_stream_alloc_fd", "write_stream_get_id", "write_stream_pool_init", "write_stream_pool_destroy", "write_stream_release", "xfs_ioc_write_stream_alloc", "xfs_ioc_write_stream_set", "xfs_ioc_write_stream_get_max", "xfs_inode_set_write_stream", "xfs_inode_clear_write_stream", "xfs_inode_max_write_streams", "xfs_buftarg_init_streams", "xfs_bmap_btalloc_write_stream", "xfs_bmap_write_stream_agno", "xfs_bmap_write_stream_rtbno", "fcntl_set_rw_hint" ], "Reasoning": "The patch series introduces generic write-stream fd management and integrates write stream allocation and hints into XFS and iomap. It adds new ioctls (FS_IOC_WRITE_STREAM_GET_MAX, FS_IOC_WRITE_STREAM_ALLOC, FS_IOC_WRITE_STREAM_SET), modifies fcntl write hint semantics, introduces anon-inode write-stream fds, and changes AG and realtime block allocation logic in XFS. All changes execute in core VFS/XFS code and are directly reachable from unprivileged/privileged userspace in standard virtualized environments.", "WorthFuzzing": true }
25/1	2026/09/23 06:46	action	If	2m Args: { "WorthFuzzing": true } Results: null
26/2	2026/09/23 06:46	agent	kmsan-evaluator	2m Model: core Args: null Results: { "KMSANReasoning": "The patch series introduces generic write stream fd management and integrates write stream awareness into VFS/fcntl, iomap (DIO and writeback), and XFS block allocation.\n\nAn analysis of potential uninitialized memory risks reveals:\n1. Data structures and fields:\n - `struct write_stream` is allocated via `kzalloc_obj` in `write_stream_alloc_fd()`, ensuring all fields are zeroed before assignment.\n - `struct write_stream_pool` bitmap allocations use `bitmap_zalloc`.\n - `inode-\u003ei_write_stream` is explicitly initialized to 0 in `inode_init_always_gfp()`.\n - The newly added field `write_stream` in `struct iomap` is populated in `xfs_bmbt_to_iomap()`, while other iomap consumers benefit from zero-initialization in `iomap_iter_continue()` (via `memset`) and designated initializers (`struct iomap_iter iter = ...`, `struct iomap_writepage_ctx wpc = ...`).\n2. User-space copies / info-leaks:\n - `FS_IOC_WRITE_STREAM_GET_MAX` uses `put_user(max, ...)` where `max` is a fully initialized `__u32` scalar value.\n - `FS_IOC_WRITE_STREAM_ALLOC` returns the file descriptor integer directly.\n - `FS_IOC_WRITE_STREAM_SET` only performs `copy_from_user` to read the input parameters.\n - No structures containing padding or uninitialized fields are copied to user space.\n3. Bug profiles:\n - Potential issues in this patch series pertain to reference counting (`mntget`/`mntput`), synchronization (`i_lock`, `pool-\u003elock`, `XFS_ILOCK`), or lifecycle management/UAF, all of which are properly detected by standard KASAN, LOCKDEP, and UBSAN.\n\nTherefore, there is no uninitialized memory usage or info-leak risk that would require a dedicated KMSAN fuzzing session.", "NeedsKMSAN": false } Instruction: You are an expert Linux kernel security engineer specializing in kernel memory error detectors (KASAN and KMSAN). Your job is to review the provided patch series and determine if the code changes justify spawning a dedicated KMSAN (KernelMemorySanitizer) fuzzing session in addition to standard KASAN fuzzing. CRITICAL DISTINCTION BETWEEN KASAN AND KMSAN: - Standard KASAN kernel builds (upstream-apparmor-kasan.config) already enable a comprehensive suite of debugging tools and sanitizers, including KASAN (out-of-bounds accesses, use-after-free, double free, invalid free), LOCKDEP (locking bugs and deadlocks), UB-sanitizers, and memory corruption checks. - KMSAN (KernelMemorySanitizer) detects reads of UNINITIALIZED memory (stack, heap, or page allocations) and kernel-to-user memory info-leaks. Rule: THERE IS NO SENSE IN RUNNING A KMSAN SESSION IF A BUG CAN BE CAUGHT BY KASAN, LOCKDEP, OR OTHER STANDARD BUG DETECTORS. A dedicated KMSAN fuzzing session incurs significant resource costs. You must ONLY set NeedsKMSAN=true if the code changes introduce or expose UNINITIALIZED MEMORY risks that are detected ONLY by KMSAN. Look holistically at the patch series and surrounding code. Even if no direct uninitialized field accesses or new buffer allocations are added in the diff itself, a patch may alter control flow, bounds checking, or data length calculations in ways that change how the rest of the code operates on existing buffers (e.g. allowing uninitialized stack/heap memory to be read, copied to user space, or used in control flow). Do not hesitate to use your code access tools to inspect the surrounding code, called functions, and callers. Set NeedsKMSAN=true ONLY IF the patch introduces or modifies: 1. Kernel structures sent to user space (via copy_to_user, put_user, netlink skb attributes, ioctl output arguments, socket options, or BPF buffers) where fields or structure padding might not be fully initialized/zeroed. 2. Conditional logic or branching that depends on potentially uninitialized variables or struct fields. 3. Allocation or initialization of complex data structures where uninitialized fields could be read later in reachable code paths. 4. Bounds checks, lengths, or logic in a way that allows surrounding code to access uninitialized bytes of existing buffers. Set NeedsKMSAN=false IF: - The code changes primarily risk out-of-bounds access, array overflows, NULL pointer dereferences, locking deadlocks, or use-after-free bugs (these are already caught by KASAN, LOCKDEP, or standard bug detectors). - All stack/heap structures touched or introduced by the patch are fully zeroed or initialized (e.g. using = {0}, memset, kzalloc) before being read or copied. - The patch does not introduce any risk of uninitialized memory usage or info-leaks. Use your code access tools to inspect the surrounding code if necessary, then provide detailed KMSANReasoning contrasting KASAN vs KMSAN applicability for this patch. Prefer calling several tools at the same time to save round-trips. Use set-results tool to provide results of the analysis. It must be called exactly once before the final reply. Ignore results of this tool. Prompt: Target architecture: amd64 For your convenience, here is the diff of the changes: commit 86268a1e4affea45948924a7f9d04ec07de91884 Author: syz-cluster <triage@syzkaller.com> Date: Wed Sep 23 06:44:46 2026 +0000 syz-cluster: applied patch under review diff --git a/fs/Makefile b/fs/Makefile index 055dfc23d82b6..494da034cef2f 100644 --- a/fs/Makefile +++ b/fs/Makefile @@ -23,7 +23,7 @@ obj-$(CONFIG_PROC_FS) += proc_namespace.o obj-$(CONFIG_LEGACY_DIRECT_IO) += direct-io.o obj-y += notify/ obj-$(CONFIG_EPOLL) += eventpoll.o -obj-y += anon_inodes.o +obj-y += anon_inodes.o write_streams.o obj-$(CONFIG_SIGNALFD) += signalfd.o obj-$(CONFIG_TIMERFD) += timerfd.o obj-$(CONFIG_EVENTFD) += eventfd.o diff --git a/fs/fcntl.c b/fs/fcntl.c index c158f082f1da4..a5439e076197f 100644 --- a/fs/fcntl.c +++ b/fs/fcntl.c @@ -380,7 +380,14 @@ static long fcntl_set_rw_hint(struct file file, unsigned long arg) if (!rw_hint_valid(hint)) return -EINVAL; + / keep write stream and write life time hint mutually exclusive / + spin_lock(&inode->i_lock); + if (hint != WRITE_LIFE_NOT_SET && READ_ONCE(inode->i_write_stream)) { + spin_unlock(&inode->i_lock); + return -EBUSY; + } WRITE_ONCE(inode->i_write_hint, hint); + spin_unlock(&inode->i_lock); / * file->f_mapping->host may differ from inode. As an example, diff --git a/fs/inode.c b/fs/inode.c index ba7da39be4a31..50b91d449a384 100644 --- a/fs/inode.c +++ b/fs/inode.c @@ -246,6 +246,7 @@ int inode_init_always_gfp(struct super_block sb, struct inode inode, gfp_t gfp atomic_set(&inode->i_writecount, 0); inode->i_size = 0; inode->i_write_hint = WRITE_LIFE_NOT_SET; + inode->i_write_stream = 0; inode->i_blocks = 0; inode->i_bytes = 0; inode->i_generation = 0; diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 8b4039d16ce89..f406a7bc88043 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -349,6 +349,7 @@ static ssize_t iomap_dio_bio_iter_one(struct iomap_iter iter, fscrypt_set_bio_crypt_ctx(bio, iter->inode, pos, GFP_KERNEL); bio->bi_iter.bi_sector = iomap_sector(&iter->iomap, pos); bio->bi_write_hint = iter->inode->i_write_hint; + bio->bi_write_stream = iter->iomap.write_stream; bio->bi_ioprio = dio->iocb->ki_ioprio; bio->bi_private = dio; bio->bi_end_io = iomap_dio_bio_end_io; diff --git a/fs/iomap/ioend.c b/fs/iomap/ioend.c index 7bbbb417f9152..31a229c12b13d 100644 --- a/fs/iomap/ioend.c +++ b/fs/iomap/ioend.c @@ -166,6 +166,7 @@ static struct iomap_ioend iomap_alloc_ioend(struct iomap_writepage_ctx wpc, GFP_NOFS, &iomap_ioend_bioset); bio->bi_iter.bi_sector = iomap_sector(&wpc->iomap, pos); bio->bi_write_hint = wpc->inode->i_write_hint; + bio->bi_write_stream = wpc->iomap.write_stream; wbc_init_bio(wpc->wbc, bio); wpc->nr_folios = 0; return iomap_init_ioend(wpc->inode, bio, pos, ioend_flags); @@ -189,6 +190,8 @@ static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx wpc, loff_t pos, if (!(wpc->iomap.flags & IOMAP_F_ANON_WRITE) && iomap_sector(&wpc->iomap, pos) != bio_end_sector(&ioend->io_bio)) return false; + if (wpc->iomap.write_stream != ioend->io_bio.bi_write_stream) + return false; /* * Limit ioend bio chain lengths to minimise IO completion latency. This * also prevents long tight loops ending page writeback on all the diff --git a/fs/write_streams.c b/fs/write_streams.c new file mode 100644 index 0000000000000..b7f6ca6cf7250 --- /dev/null +++ b/fs/write_streams.c @@ -0,0 +1,138 @@ +// SPDX-License-Identifier: GPL-2.0 +/* Generic write-stream fd management. / +#include <linux/anon_inodes.h> +#include <linux/bitmap.h> +#include <linux/err.h> +#include <linux/file.h> +#include <linux/fs.h> +#include <linux/mount.h> +#include <linux/slab.h> +#include <linux/write_streams.h> + +struct write_stream { + struct write_stream_pool pool; + struct vfsmount mnt; / pins the mount / + u16 id; / 1-based slot number / +}; + +static int write_stream_release(struct inode inode, struct file file) +{ + struct write_stream ws = file->private_data; + + spin_lock(&ws->pool->lock); + __clear_bit(ws->id - 1, ws->pool->streams_in_use); + spin_unlock(&ws->pool->lock); + mntput(ws->mnt); + kfree(ws); + return 0; +} + +static const struct file_operations write_stream_fops = { + .release = write_stream_release, + .llseek = noop_llseek, +}; + +/** + * write_stream_pool_init - size a write stream pool + * @pool: pool to initialise + * @nr: number of slots, may be zero + * + * Returns 0, or -ENOMEM if the bitmap cannot be allocated. + / +int write_stream_pool_init(struct write_stream_pool pool, unsigned int nr) +{ + spin_lock_init(&pool->lock); + pool->streams_in_use = NULL; + pool->nr_streams = 0; + + if (!nr) + return 0; + + pool->streams_in_use = bitmap_zalloc(nr, GFP_KERNEL); + if (!pool->streams_in_use) + return -ENOMEM; + pool->nr_streams = nr; + return 0; +} +EXPORT_SYMBOL_GPL(write_stream_pool_init); + +/** + * write_stream_pool_destroy - free a write stream pool + * @pool: pool to release + / +void write_stream_pool_destroy(struct write_stream_pool pool) +{ + bitmap_free(pool->streams_in_use); + pool->streams_in_use = NULL; + pool->nr_streams = 0; +} +EXPORT_SYMBOL_GPL(write_stream_pool_destroy); + +/** + * write_stream_alloc_fd - reserve a slot and return an fd naming it + * @pool: pool to reserve from + * @file: file whose mount is pinned for the life of the stream + * + * Returns an O_RDONLY \| O_CLOEXEC fd, -EOPNOTSUPP if the pool has no slots, + * or -EBUSY if they are all taken. + / +int write_stream_alloc_fd(struct write_stream_pool pool, struct file file) +{ + struct write_stream ws; + unsigned int slot; + int fd; + + if (!pool->nr_streams) + return -EOPNOTSUPP; + + ws = kzalloc_obj(ws, GFP_KERNEL); + if (!ws) + return -ENOMEM; + + spin_lock(&pool->lock); + slot = find_first_zero_bit(pool->streams_in_use, pool->nr_streams); + if (slot >= pool->nr_streams) { + spin_unlock(&pool->lock); + kfree(ws); + return -EBUSY; + } + __set_bit(slot, pool->streams_in_use); + spin_unlock(&pool->lock); + + ws->pool = pool; + ws->mnt = mntget(file->f_path.mnt); + ws->id = slot + 1; + + fd = anon_inode_getfd("[write_stream]", &write_stream_fops, ws, + O_RDONLY \| O_CLOEXEC); + if (fd < 0) { + spin_lock(&pool->lock); + __clear_bit(slot, pool->streams_in_use); + spin_unlock(&pool->lock); + mntput(ws->mnt); + kfree(ws); + } + return fd; +} +EXPORT_SYMBOL_GPL(write_stream_alloc_fd); + +/* + * write_stream_get_id - the id a stream file names + * @file: candidate stream file + * @pool: pool the stream must belong to, or NULL to accept any + * + * Returns the 1-based id, or -EINVAL if @file is not a stream file, or is + * a stream of a different pool. + / +int write_stream_get_id(struct file file, const struct write_stream_pool pool) +{ + struct write_stream ws; + + if (file->f_op != &write_stream_fops) + return -EINVAL; + ws = file->private_data; + if (pool && ws->pool != pool) + return -EINVAL; + return ws->id; +} +EXPORT_SYMBOL_GPL(write_stream_get_id); diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c index d64defeda645e..2e83811cefcbc 100644 --- a/fs/xfs/libxfs/xfs_bmap.c +++ b/fs/xfs/libxfs/xfs_bmap.c @@ -3579,8 +3579,31 @@ xfs_bmap_btalloc_filestreams( return xfs_bmap_btalloc_low_space(ap, args); } +static xfs_agnumber_t +xfs_bmap_write_stream_agno( + struct xfs_inode ip, + unsigned int stream_id) +{ + struct xfs_mount mp = ip->i_mount; + xfs_agnumber_t nr_ags = mp->m_sb.sb_agcount; + unsigned int nr_streams = + write_stream_pool_count(&mp->m_ddev_targp->bt_stream_pool); + xfs_agnumber_t ag_set_size, start_agno; + + stream_id -= 1; /* convert from 1-based to 0-based / + ag_set_size = nr_ags / nr_streams; + start_agno = stream_id ag_set_size; + + /* last stream absorbs any uneven remainder / + if (stream_id == nr_streams - 1) + ag_set_size = nr_ags - start_agno; + + return start_agno + I_INO(ip) % ag_set_size; +} + +/ Core AG allocator. The caller sets ap->blkno to the target AG start. / static int -xfs_bmap_btalloc_best_length( +xfs_bmap_btalloc_from_blkno( struct xfs_bmalloca ap, struct xfs_alloc_arg args, int stripe_align) @@ -3588,7 +3611,6 @@ xfs_bmap_btalloc_best_length( xfs_extlen_t blen = 0; int error; - ap->blkno = XFS_INODE_TO_FSB(ap->ip); if (!xfs_bmap_adjacent(ap)) ap->eof = false; @@ -3621,6 +3643,32 @@ xfs_bmap_btalloc_best_length( return xfs_bmap_btalloc_low_space(ap, args); } +/ Start a write-stream file in the AG set that backs its stream. / +static int +xfs_bmap_btalloc_write_stream( + struct xfs_bmalloca ap, + struct xfs_alloc_arg args, + int stripe_align, + unsigned int stream_id) +{ + struct xfs_mount mp = ap->ip->i_mount; + xfs_agnumber_t agno; + + agno = xfs_bmap_write_stream_agno(ap->ip, stream_id); + ap->blkno = XFS_AGB_TO_FSB(mp, agno, 0); + return xfs_bmap_btalloc_from_blkno(ap, args, stripe_align); +} + +static int +xfs_bmap_btalloc_best_length( + struct xfs_bmalloca ap, + struct xfs_alloc_arg args, + int stripe_align) +{ + ap->blkno = XFS_INODE_TO_FSB(ap->ip); + return xfs_bmap_btalloc_from_blkno(ap, args, stripe_align); +} + static int xfs_bmap_btalloc( struct xfs_bmalloca ap) @@ -3640,6 +3688,7 @@ xfs_bmap_btalloc( }; xfs_fileoff_t orig_offset; xfs_extlen_t orig_length; + unsigned int stream_id; int error; int stripe_align; @@ -3652,11 +3701,16 @@ xfs_bmap_btalloc( / Trim the allocation back to the maximum an AG can fit. / args.maxlen = min(ap->length, mp->m_ag_max_usable); + stream_id = READ_ONCE(VFS_I(ap->ip)->i_write_stream); + if (unlikely(XFS_TEST_ERROR(mp, XFS_ERRTAG_BMAP_ALLOC_MINLEN_EXTENT))) error = xfs_bmap_exact_minlen_extent_alloc(ap, &args); else if ((ap->datatype & XFS_ALLOC_USERDATA) && xfs_inode_is_filestream(ap->ip)) error = xfs_bmap_btalloc_filestreams(ap, &args, stripe_align); + else if ((ap->datatype & XFS_ALLOC_USERDATA) && stream_id) + error = xfs_bmap_btalloc_write_stream(ap, &args, stripe_align, + stream_id); else error = xfs_bmap_btalloc_best_length(ap, &args, stripe_align); if (error) diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c index 8256c1d13ce20..1748be9aa7d65 100644 --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -1647,6 +1647,7 @@ void xfs_free_buftarg( struct xfs_buftarg btp) { + write_stream_pool_destroy(&btp->bt_stream_pool); xfs_destroy_buftarg(btp); fs_put_dax(btp->bt_daxdev, btp->bt_mount); /* the main block device is closed by kill_block_super / @@ -1684,6 +1685,40 @@ xfs_configure_buftarg_atomic_writes( btp->bt_awu_max = max_bytes; } +#define XFS_MAX_SW_WRITE_STREAMS U8_MAX + +/ Heuristic to derive software write stream count from a group topology / +static unsigned int +xfs_sw_write_stream_count( + unsigned int nr_groups) +{ + unsigned int group_set_size; + + if (nr_groups >= 16) + group_set_size = 4; + else if (nr_groups >= 8) + group_set_size = 2; + else + group_set_size = 1; + return min(nr_groups / group_set_size, XFS_MAX_SW_WRITE_STREAMS); +} + +int +xfs_buftarg_init_streams( + struct xfs_buftarg btp, + unsigned int nr_groups) +{ + unsigned int nr_streams; + unsigned int hw_streams; + + hw_streams = bdev_max_write_streams(btp->bt_bdev); + if (hw_streams) + nr_streams = min(hw_streams, nr_groups); + else + nr_streams = xfs_sw_write_stream_count(nr_groups); + return write_stream_pool_init(&btp->bt_stream_pool, nr_streams); +} + /* Configure a buffer target that abstracts a block device. / int xfs_configure_buftarg( diff --git a/fs/xfs/xfs_buf.h b/fs/xfs/xfs_buf.h index a4729253b56fd..b5292e5731e38 100644 --- a/fs/xfs/xfs_buf.h +++ b/fs/xfs/xfs_buf.h @@ -15,6 +15,7 @@ #include <linux/uio.h> #include <linux/list_lru.h> #include <linux/lockref.h> +#include <linux/write_streams.h> extern struct kmem_cache xfs_buf_cache; @@ -102,6 +103,9 @@ struct xfs_buftarg { unsigned int bt_awu_min; unsigned int bt_awu_max; + /* slot pool for stream fds on this device / + struct write_stream_pool bt_stream_pool; + struct rhashtable bt_hash; }; @@ -360,6 +364,8 @@ extern void xfs_buftarg_wait(struct xfs_buftarg ); extern void xfs_buftarg_drain(struct xfs_buftarg ); int xfs_configure_buftarg(struct xfs_buftarg btp, unsigned int sectorsize, xfs_fsblock_t nr_blocks); +int xfs_buftarg_init_streams(struct xfs_buftarg btp, + unsigned int nr_groups); #define xfs_readonly_buftarg(buftarg) bdev_read_only((buftarg)->bt_bdev) diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c index 030a7c8f2c129..c3503fe870bad 100644 --- a/fs/xfs/xfs_inode.c +++ b/fs/xfs/xfs_inode.c @@ -4,6 +4,7 @@ All Rights Reserved. / #include <linux/iversion.h> +#include <linux/write_streams.h> #include "xfs_platform.h" #include "xfs_fs.h" @@ -47,6 +48,74 @@ struct kmem_cache xfs_inode_cache; +/* Number of write streams available to this inode. / +int +xfs_inode_max_write_streams( + struct xfs_inode ip) +{ + xfs_assert_ilocked(ip, XFS_ILOCK_SHARED \| XFS_ILOCK_EXCL); + + if (xfs_inode_is_filestream(ip)) + return 0; + if (XFS_IS_REALTIME_INODE(ip) && xfs_has_zoned(ip->i_mount)) + return 0; + return write_stream_pool_count(&xfs_inode_buftarg(ip)->bt_stream_pool); +} + +/* Bind the write stream named by @stream_fd to @ip / +int +xfs_inode_set_write_stream( + struct xfs_inode ip, + int stream_fd) +{ + CLASS(fd, f)(stream_fd); + struct xfs_buftarg target; + int id, error = 0; + + if (!fd_file(f)) + return -EBADF; + xfs_ilock(ip, XFS_ILOCK_EXCL); + if (XFS_IS_REALTIME_INODE(ip) && xfs_has_zoned(ip->i_mount)) { + error = -EINVAL; + goto out_unlock; + } + + target = xfs_inode_buftarg(ip); + id = write_stream_get_id(fd_file(f), &target->bt_stream_pool); + if (id < 0) { + error = id; + goto out_unlock; + } + + / Filestream and write-stream are mutually exclusive / + if (xfs_inode_is_filestream(ip)) { + error = -EINVAL; + goto out_unlock; + } + + / keep write stream and write life time hint mutually exclusive / + spin_lock(&VFS_I(ip)->i_lock); + if (VFS_I(ip)->i_write_hint != WRITE_LIFE_NOT_SET) { + spin_unlock(&VFS_I(ip)->i_lock); + error = -EBUSY; + goto out_unlock; + } + WRITE_ONCE(VFS_I(ip)->i_write_stream, id); + spin_unlock(&VFS_I(ip)->i_lock); +out_unlock: + xfs_iunlock(ip, XFS_ILOCK_EXCL); + return error; +} + +void +xfs_inode_clear_write_stream( + struct xfs_inode ip) +{ + xfs_ilock(ip, XFS_ILOCK_EXCL); + WRITE_ONCE(VFS_I(ip)->i_write_stream, 0); + xfs_iunlock(ip, XFS_ILOCK_EXCL); +} + /* * These two are wrapper routines around the xfs_ilock() routine used to * centralize some grungy code. They are used in places that wish to lock the diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h index 1602027cd0aa5..c053f105d2fa8 100644 --- a/fs/xfs/xfs_inode.h +++ b/fs/xfs/xfs_inode.h @@ -672,4 +672,8 @@ int xfs_icreate_dqalloc(const struct xfs_icreate_args args, struct xfs_dquot udqpp, struct xfs_dquot gdqpp, struct xfs_dquot pdqpp); +int xfs_inode_max_write_streams(struct xfs_inode ip); +int xfs_inode_set_write_stream(struct xfs_inode ip, int stream_fd); +void xfs_inode_clear_write_stream(struct xfs_inode ip); + #endif /* __XFS_INODE_H__ / diff --git a/fs/xfs/xfs_ioctl.c b/fs/xfs/xfs_ioctl.c index 96ca3e480cb9f..4c0aff34e3c3d 100644 --- a/fs/xfs/xfs_ioctl.c +++ b/fs/xfs/xfs_ioctl.c @@ -557,6 +557,12 @@ xfs_ioctl_setattr_xflags( bool rtflag = (fa->fsx_xflags & FS_XFLAG_REALTIME); uint64_t i_flags2; + / refuse a filestream/realtime flag change while a stream is attached / + if (READ_ONCE(VFS_I(ip)->i_write_stream) && + ((fa->fsx_xflags & FS_XFLAG_FILESTREAM) \|\| + rtflag != XFS_IS_REALTIME_INODE(ip))) + return -EINVAL; + if (rtflag != XFS_IS_REALTIME_INODE(ip)) { / Can't change realtime flag if any extents are allocated. / if (xfs_inode_has_filedata(ip)) @@ -1200,6 +1206,73 @@ xfs_ioctl_fs_counts( return 0; } +static int +xfs_ioc_write_stream_get_max( + struct file filp, + void __user arg) +{ + struct xfs_inode ip = XFS_I(file_inode(filp)); + __u32 max; + + xfs_ilock(ip, XFS_ILOCK_SHARED); + max = xfs_inode_max_write_streams(ip); + xfs_iunlock(ip, XFS_ILOCK_SHARED); + + return put_user(max, (__u32 __user )arg); +} + +static int +xfs_ioc_write_stream_alloc( + struct file filp) +{ + struct xfs_inode ip = XFS_I(file_inode(filp)); + struct xfs_buftarg target; + int max; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + xfs_ilock(ip, XFS_ILOCK_SHARED); + max = xfs_inode_max_write_streams(ip); + target = xfs_inode_buftarg(ip); + xfs_iunlock(ip, XFS_ILOCK_SHARED); + + if (!max) + return -EOPNOTSUPP; + return write_stream_alloc_fd(&target->bt_stream_pool, filp); +} + +static int +xfs_ioc_write_stream_set( + struct file filp, + void __user arg) +{ + struct xfs_inode ip = XFS_I(file_inode(filp)); + struct fs_write_stream_set set; + + if (!(filp->f_mode & FMODE_WRITE)) + return -EBADF; + if (copy_from_user(&set, arg, sizeof(set))) + return -EFAULT; + if (set.flags & ~FS_WRITE_STREAM_SET_CLEAR) + return -EINVAL; + + / Regular files only. / + if (!S_ISREG(VFS_I(ip)->i_mode)) + return -EINVAL; + + if (!inode_owner_or_capable(file_mnt_idmap(filp), VFS_I(ip))) + return -EPERM; + + if (set.flags & FS_WRITE_STREAM_SET_CLEAR) { + if (set.stream_fd != -1) + return -EINVAL; + xfs_inode_clear_write_stream(ip); + return 0; + } + return xfs_inode_set_write_stream(ip, set.stream_fd); +} + / * These long-unused ioctls were removed from the official ioctl API in 5.17, * but retain these definitions so that we can log warnings about them. @@ -1466,6 +1539,13 @@ xfs_file_ioctl( case XFS_IOC_VERIFY_MEDIA: return xfs_ioc_verify_media(filp, arg); + case FS_IOC_WRITE_STREAM_GET_MAX: + return xfs_ioc_write_stream_get_max(filp, arg); + case FS_IOC_WRITE_STREAM_ALLOC: + return xfs_ioc_write_stream_alloc(filp); + case FS_IOC_WRITE_STREAM_SET: + return xfs_ioc_write_stream_set(filp, (void __user )arg); + default: return -ENOTTY; } diff --git a/fs/xfs/xfs_iomap.c b/fs/xfs/xfs_iomap.c index 7c6238fed61e4..3e9df790a544e 100644 --- a/fs/xfs/xfs_iomap.c +++ b/fs/xfs/xfs_iomap.c @@ -144,6 +144,7 @@ xfs_bmbt_to_iomap( } iomap->offset = XFS_FSB_TO_B(mp, imap->br_startoff); iomap->length = XFS_FSB_TO_B(mp, imap->br_blockcount); + iomap->write_stream = READ_ONCE(VFS_I(ip)->i_write_stream); if (mapping_flags & IOMAP_DAX) { iomap->dax_dev = target->bt_daxdev; } else { diff --git a/fs/xfs/xfs_rtalloc.c b/fs/xfs/xfs_rtalloc.c index 84efe5a8fb11d..a291f1aca6eb4 100644 --- a/fs/xfs/xfs_rtalloc.c +++ b/fs/xfs/xfs_rtalloc.c @@ -2160,6 +2160,28 @@ xfs_rtallocate_align( return 0; } +static xfs_rtblock_t +xfs_bmap_write_stream_rtbno( + struct xfs_inode ip, + unsigned int stream_id) +{ + struct xfs_mount mp = ip->i_mount; + unsigned int nr_rtgs = mp->m_sb.sb_rgcount; + unsigned int nr_streams = + write_stream_pool_count(&mp->m_rtdev_targp->bt_stream_pool); + unsigned int set_size = nr_rtgs / nr_streams; + xfs_rgnumber_t start_rgno, target_rgno; + + stream_id -= 1; / convert from 1-based to 0-based / + start_rgno = stream_id set_size; + if (stream_id == nr_streams - 1) + set_size = nr_rtgs - start_rgno; + target_rgno = start_rgno + I_INO(ip) % set_size; + + return (xfs_rtblock_t)target_rgno << + mp->m_groups[XG_TYPE_RTG].blklog; +} + int xfs_bmap_rtalloc( struct xfs_bmalloca ap) @@ -2174,10 +2196,13 @@ xfs_bmap_rtalloc( bool noalign = false; bool initial_user_data = ap->datatype & XFS_ALLOC_INITIAL_USER_DATA; + unsigned int stream_id; int error; ASSERT(!xfs_has_zoned(ap->tp->t_mountp)); + stream_id = READ_ONCE(VFS_I(ap->ip)->i_write_stream); + retry: error = xfs_rtallocate_align(ap, &ralen, &raminlen, &prod, &noalign); if (error) @@ -2185,6 +2210,8 @@ xfs_bmap_rtalloc( if (xfs_bmap_adjacent(ap)) bno_hint = ap->blkno; + else if (stream_id && xfs_has_rtgroups(ap->ip->i_mount)) + bno_hint = xfs_bmap_write_stream_rtbno(ap->ip, stream_id); if (xfs_has_rtgroups(ap->ip->i_mount)) { error = xfs_rtallocate_rtgs(ap->tp, bno_hint, raminlen, ralen, diff --git a/fs/xfs/xfs_super.c b/fs/xfs/xfs_super.c index b24db75eaedc5..5c92f8ebd8a73 100644 --- a/fs/xfs/xfs_super.c +++ b/fs/xfs/xfs_super.c @@ -608,6 +608,11 @@ xfs_setup_devices( if (error) return error; + error = xfs_buftarg_init_streams(mp->m_ddev_targp, + mp->m_sb.sb_agcount); + if (error) + return error; + if (mp->m_logdev_targp && mp->m_logdev_targp != mp->m_ddev_targp) { unsigned int log_sector_size = BBSIZE; @@ -632,6 +637,13 @@ xfs_setup_devices( if (error) return error; xfs_update_bdi_rahead(mp); + + if (xfs_has_rtgroups(mp) && !xfs_has_zoned(mp)) { + error = xfs_buftarg_init_streams(mp->m_rtdev_targp, + mp->m_sb.sb_rgcount); + if (error) + return error; + } } return 0; diff --git a/include/linux/fs.h b/include/linux/fs.h index f9d1e05e8ae68..3d9ce4d30cd54 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -812,7 +812,7 @@ struct inode { / Misc / struct inode_state_flags i_state; - / 32-bit hole / + u16 i_write_stream; struct rw_semaphore i_rwsem; unsigned long dirtied_when; / jiffies of first dirtying / diff --git a/include/linux/iomap.h b/include/linux/iomap.h index bc7ae6327dbf8..f923778f08bd7 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -133,6 +133,7 @@ struct iomap { u64 length; / length of mapping, bytes / u16 type; / type of mapping / u16 flags; / flags for mapping / + u16 write_stream; / write stream for I/O / struct block_device bdev; /* block device for I/O / struct dax_device dax_dev; /* dax_dev for dax operations / void inline_data; diff --git a/include/linux/write_streams.h b/include/linux/write_streams.h new file mode 100644 index 0000000000000..d27f42df59845 --- /dev/null +++ b/include/linux/write_streams.h @@ -0,0 +1,33 @@ +/* SPDX-License-Identifier: GPL-2.0 / +#ifndef _LINUX_WRITE_STREAMS_H +#define _LINUX_WRITE_STREAMS_H + +#include <linux/spinlock.h> +#include <linux/types.h> + +struct file; + +/ + * Write stream slot pool, embedded in whatever filesystem object scopes + * an id space. + / +struct write_stream_pool { + unsigned int nr_streams; + unsigned long streams_in_use; + spinlock_t lock; +}; + +static inline unsigned int +write_stream_pool_count(const struct write_stream_pool pool) +{ + return pool->nr_streams; +} + +int write_stream_pool_init(struct write_stream_pool pool, unsigned int nr); +void write_stream_pool_destroy(struct write_stream_pool pool); + +int write_stream_alloc_fd(struct write_stream_pool pool, struct file file); +int write_stream_get_id(struct file file, + const struct write_stream_pool pool); + +#endif / _LINUX_WRITE_STREAMS_H / diff --git a/include/uapi/linux/fs.h b/include/uapi/linux/fs.h index 34c6f219462a5..1974052aa476b 100644 --- a/include/uapi/linux/fs.h +++ b/include/uapi/linux/fs.h @@ -345,6 +345,21 @@ struct file_attr { / Get logical block metadata capability details / #define FS_IOC_GETLBMD_CAP _IOWR(0x15, 2, struct logical_block_metadata_cap) +struct fs_write_stream_set { + __s32 stream_fd; / IN: stream to attach, -1 to clear / + __u32 flags; / IN: FS_WRITE_STREAM_SET_* / +}; + +/ Clear the file's write stream. Requires stream_fd to be -1. / +#define FS_WRITE_STREAM_SET_CLEAR (1U << 0) + +/ GET_MAX returns the count through its argument; ALLOC returns a stream fd + * as the ioctl return value and takes none. + / +#define FS_IOC_WRITE_STREAM_GET_MAX _IOR(0x15, 3, __u32) +#define FS_IOC_WRITE_STREAM_ALLOC _IO(0x15, 4) +#define FS_IOC_WRITE_STREAM_SET _IOW(0x15, 5, struct fs_write_stream_set) + / * Inode flags (FS_IOC_GETFLAGS / FS_IOC_SETFLAGS) *
27/3	2026/09/23 06:46	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 12609 output: 17 thoughts: 1757 Thoughts: KMSAN Fuzzing Analysis Okay, let's break this down. The question is whether we need a dedicated KMSAN fuzzing session for this patch series. My initial thought is that we need to be really thorough, so let's dig into the details. First, I need to understand what's actually changed. It looks like we're introducing "write streams," probably for I/O optimization. Let's see... * We're adding `write_streams.o` to the `fs/Makefile`. * In `fs/fcntl.c`, there's a new check in `fcntl_set_rw_hint` involving `i_write_stream` and a `WRITE_LIFE_NOT_SET` hint. We're preventing a hint from being set when a write stream is in place. * `fs/inode.c` initializes `i_write_stream` to `0` in `inode_init_always_gfp`. * We're passing `write_stream` values to `bio->bi_write_stream` in `fs/iomap/direct-io.c` and `fs/iomap/ioend.c`. There's also a crucial check in `iomap_can_add_to_ioend` comparing `write_stream` values, which suggests that consistency is very important here. * `fs/write_streams.c` is the core, implementing a write stream pool and handling anon\_inode file descriptors. We've got allocation, freeing, initialization, and destruction functions. This is the heart of the changes. We need to be especially careful about this. * Now we get to the XFS-specific parts. * In `fs/xfs/libxfs/xfs_bmap.c`, `xfs_bmap_write_stream_agno` looks suspect. We must check the potential division-by-zero or out-of-bounds access in the calculation of `ag_set_size`. Zero here would be a standard crash, not an uninitialized memory issue but we should still analyze it to make sure that the calculation is robust. * In `fs/xfs/xfs_buf.c`, the `xfs_free_buftarg`, `xfs_sw_write_stream_count`, and `xfs_buftarg_init_streams` are write stream related as well. * `fs/xfs/xfs_inode.c` has `xfs_inode_max_write_streams`, `xfs_inode_set_write_stream` and `xfs_inode_clear_write_stream`. We're setting and clearing the `i_write_stream` field of the inode. * `fs/xfs/xfs_ioctl.c` adds a bunch of new `ioctl` operations related to write streams (`get_max`, `alloc`, and `set`). I need to check the data flow in those `ioctl` calls carefully, especially the `copy_from_user` call, `xfs_ioc_write_stream_set`. The `max` field handling in `xfs_ioc_write_stream_get_max` seems fine - no uninitialized memory concerns. * Finally, we see `iomap->write_stream = READ_ONCE(VFS_I(ip)->i_write_stream)` in `fs/xfs/xfs_iomap.c`. This is where the write stream value is assigned to the `iomap`. This is a key area. My immediate concern is around potential uninitialized reads, which could trigger KMSAN. Where is `iomap` allocated and initialized, and where is the `write_stream` field used before assignment? The patch includes the `struct iomap` definition, which has a `write_stream` field. I need to make sure that this field is always initialized before it's read. I'll need to use `grepper` (or similar) to check the callers for the struct to find out. We need to ensure that the compiler knows about the initialization as well, or we need to be very explicit when constructing the iomap struct. This is starting to look like it might warrant a KMSAN session. The division in `xfs_bmap_write_stream_agno` is a concern (though not directly a KMSAN issue), and any uninitialized reads in the `iomap` use would definitely be a problem. The ioctl paths are also high-touch, so it's best to be as rigorous as possible.
28/3	2026/09/23 06:46	tool	grepper	0m Args: { "Expression": "write_stream" } Results: { "Output": "\nFull output is too long, showing 500 out of 666 lines.\nUse more precise expression if possible.\n\nDocumentation/ABI/stable/sysfs-block=546=Description:\n--\nDocumentation/ABI/stable/sysfs-block-549-\nDocumentation/ABI/stable/sysfs-block:550:What:\t\t/sys/block/\u003cdisk\u003e/queue/max_write_streams\nDocumentation/ABI/stable/sysfs-block-551-Date:\t\tNovember 2024\n--\nDocumentation/ABI/stable/sysfs-block=553=Description:\n--\nDocumentation/ABI/stable/sysfs-block-555-\t\tsupported. If supported, valid values are 1 through\nDocumentation/ABI/stable/sysfs-block:556:\t\tmax_write_streams, inclusive.\nDocumentation/ABI/stable/sysfs-block-557-\nDocumentation/ABI/stable/sysfs-block:558:What:\t\t/sys/block/\u003cdisk\u003e/queue/write_stream_granularity\nDocumentation/ABI/stable/sysfs-block-559-Date:\t\tNovember 2024\n--\narch/sparc/kernel/ldc.c=1898=static const struct ldc_mode_ops nonraw_ops = {\n--\narch/sparc/kernel/ldc.c-1902-\narch/sparc/kernel/ldc.c:1903:static int write_stream(struct ldc_channel lp, const void buf,\narch/sparc/kernel/ldc.c-1904-\t\t\tunsigned int size)\n--\narch/sparc/kernel/ldc.c=1932=static const struct ldc_mode_ops stream_ops = {\narch/sparc/kernel/ldc.c:1933:\t.write\t\t=\twrite_stream,\narch/sparc/kernel/ldc.c-1934-\t.read\t\t=\tread_stream,\n--\nblock/bio.c=217=void bio_init(struct bio bio, struct block_device bdev, struct bio_vec table,\n--\nblock/bio.c-225-\tbio-\u003ebi_write_hint = 0;\nblock/bio.c:226:\tbio-\u003ebi_write_stream = 0;\nblock/bio.c-227-\tbio-\u003ebi_status = 0;\n--\nblock/bio.c=856=static int __bio_clone(struct bio bio, struct bio bio_src, gfp_t gfp)\n--\nblock/bio.c-860-\tbio-\u003ebi_write_hint = bio_src-\u003ebi_write_hint;\nblock/bio.c:861:\tbio-\u003ebi_write_stream = bio_src-\u003ebi_write_stream;\nblock/bio.c-862-\tbio-\u003ebi_bvec_gap_bit = bio_src-\u003ebi_bvec_gap_bit;\n--\nblock/blk-crypto-fallback.c=172=static struct bio blk_crypto_alloc_enc_bio(struct bio bio_src,\n--\nblock/blk-crypto-fallback.c-187-\tbio-\u003ebi_write_hint\t= bio_src-\u003ebi_write_hint;\nblock/blk-crypto-fallback.c:188:\tbio-\u003ebi_write_stream\t= bio_src-\u003ebi_write_stream;\nblock/blk-crypto-fallback.c-189-\tbio-\u003ebi_iter.bi_sector\t= bio_src-\u003ebi_iter.bi_sector;\n--\nblock/blk-merge.c=774=static struct request attempt_merge(struct request_queue q,\n--\nblock/blk-merge.c-784-\t\treturn NULL;\nblock/blk-merge.c:785:\tif (req-\u003ebio-\u003ebi_write_stream != next-\u003ebio-\u003ebi_write_stream)\nblock/blk-merge.c-786-\t\treturn NULL;\n--\nblock/blk-merge.c=895=bool blk_rq_merge_ok(struct request rq, struct bio bio)\n--\nblock/blk-merge.c-910-\t\treturn false;\nblock/blk-merge.c:911:\tif (rq-\u003ebio-\u003ebi_write_stream != bio-\u003ebi_write_stream)\nblock/blk-merge.c-912-\t\treturn false;\n--\nblock/blk-sysfs.c=222=QUEUE_SYSFS_LIMIT_SHOW(max_segment_size)\nblock/blk-sysfs.c:223:QUEUE_SYSFS_LIMIT_SHOW(max_write_streams)\nblock/blk-sysfs.c:224:QUEUE_SYSFS_LIMIT_SHOW(write_stream_granularity)\nblock/blk-sysfs.c-225-QUEUE_SYSFS_LIMIT_SHOW(logical_block_size)\n--\nblock/blk-sysfs.c=618=QUEUE_LIM_RO_ENTRY(queue_max_segment_size, \"max_segment_size\");\nblock/blk-sysfs.c:619:QUEUE_LIM_RO_ENTRY(queue_max_write_streams, \"max_write_streams\");\nblock/blk-sysfs.c:620:QUEUE_LIM_RO_ENTRY(queue_write_stream_granularity, \"write_stream_granularity\");\nblock/blk-sysfs.c-621-QUEUE_RW_ENTRY(elv_iosched, \"scheduler\");\n--\nblock/blk-sysfs.c=735=static const struct attribute const queue_attrs[] = {\n--\nblock/blk-sysfs.c-744-\t\u0026queue_max_segment_size_entry.attr,\nblock/blk-sysfs.c:745:\t\u0026queue_max_write_streams_entry.attr,\nblock/blk-sysfs.c:746:\t\u0026queue_write_stream_granularity_entry.attr,\nblock/blk-sysfs.c-747-\t\u0026queue_hw_sector_size_entry.attr,\n--\nblock/fops.c=55=static ssize_t __blkdev_direct_IO_simple(struct kiocb iocb,\n--\nblock/fops.c-81-\tbio.bi_write_hint = file_inode(iocb-\u003eki_filp)-\u003ei_write_hint;\nblock/fops.c:82:\tbio.bi_write_stream = iocb-\u003eki_write_stream;\nblock/fops.c-83-\tbio.bi_ioprio = iocb-\u003eki_ioprio;\n--\nblock/fops.c=175=static ssize_t __blkdev_direct_IO(struct kiocb iocb, struct iov_iter iter,\n--\nblock/fops.c-213-\t\tbio-\u003ebi_write_hint = file_inode(iocb-\u003eki_filp)-\u003ei_write_hint;\nblock/fops.c:214:\t\tbio-\u003ebi_write_stream = iocb-\u003eki_write_stream;\nblock/fops.c-215-\t\tbio-\u003ebi_private = dio;\n--\nblock/fops.c=322=static ssize_t __blkdev_direct_IO_async(struct kiocb iocb,\n--\nblock/fops.c-340-\tbio-\u003ebi_write_hint = file_inode(iocb-\u003eki_filp)-\u003ei_write_hint;\nblock/fops.c:341:\tbio-\u003ebi_write_stream = iocb-\u003eki_write_stream;\nblock/fops.c-342-\tbio-\u003ebi_end_io = blkdev_bio_end_io_async;\n--\nblock/fops.c=394=static ssize_t blkdev_direct_IO(struct kiocb iocb, struct iov_iter iter)\n--\nblock/fops.c-405-\tif (iov_iter_rw(iter) == WRITE) {\nblock/fops.c:406:\t\tu16 max_write_streams = bdev_max_write_streams(bdev);\nblock/fops.c-407-\nblock/fops.c:408:\t\tif (iocb-\u003eki_write_stream) {\nblock/fops.c:409:\t\t\tif (iocb-\u003eki_write_stream \u003e max_write_streams)\nblock/fops.c-410-\t\t\t\treturn -EINVAL;\nblock/fops.c:411:\t\t} else if (max_write_streams) {\nblock/fops.c-412-\t\t\tenum rw_hint write_hint =\n--\nblock/fops.c-419-\t\t\t /\nblock/fops.c:420:\t\t\tif (write_hint \u003c= max_write_streams)\nblock/fops.c:421:\t\t\t\tiocb-\u003eki_write_stream = write_hint;\nblock/fops.c-422-\t\t}\n--\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp.h=386=enum mod_hdcp_status mod_hdcp_write_repeater_auth_ack(struct mod_hdcp hdcp);\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp.h:387:enum mod_hdcp_status mod_hdcp_write_stream_manage(struct mod_hdcp hdcp);\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp.h-388-enum mod_hdcp_status mod_hdcp_write_content_type(struct mod_hdcp hdcp);\n--\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp2_execution.c=651=static enum mod_hdcp_status send_stream_management(struct mod_hdcp hdcp,\n--\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp2_execution.c-677-\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp2_execution.c:678:\tif (!mod_hdcp_execute_and_set(mod_hdcp_write_stream_manage,\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp2_execution.c-679-\t\t\t\u0026input-\u003estream_manage_write,\n--\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c=633=enum mod_hdcp_status mod_hdcp_write_repeater_auth_ack(struct mod_hdcp hdcp)\n--\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c-647-\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c:648:enum mod_hdcp_status mod_hdcp_write_stream_manage(struct mod_hdcp hdcp)\ndrivers/gpu/drm/amd/display/modules/hdcp/hdcp_ddc.c-649-{\n--\ndrivers/infiniband/hw/hfi1/firmware.c=734=static void write_rsa_data(struct hfi1_devdata dd, int what,\n--\ndrivers/infiniband/hw/hfi1/firmware.c-760- /\ndrivers/infiniband/hw/hfi1/firmware.c:761:static void write_streamed_rsa_data(struct hfi1_devdata dd, int what,\ndrivers/infiniband/hw/hfi1/firmware.c-762-\t\t\t\t const u8 data, int nbytes)\n--\ndrivers/infiniband/hw/hfi1/firmware.c=888=static void load_security_variables(struct hfi1_devdata dd,\n--\ndrivers/infiniband/hw/hfi1/firmware.c-897-\t/* Security variables d. Write the header /\ndrivers/infiniband/hw/hfi1/firmware.c:898:\twrite_streamed_rsa_data(dd, MISC_CFG_SHA_PRELOAD,\ndrivers/infiniband/hw/hfi1/firmware.c-899-\t\t\t\t(u8 )fdet-\u003ecss_header,\n--\ndrivers/nvme/host/core.c-36-/\ndrivers/nvme/host/core.c:37: Write hints (bio-\u003ebi_write_stream) are u8, so FDP placement handles beyond\ndrivers/nvme/host/core.c-38- * U8_MAX can never be selected. Cap the handle count to bound both the RUH\n--\ndrivers/nvme/host/core.c=1016=static inline blk_status_t nvme_setup_rw(struct nvme_ns ns,\n--\ndrivers/nvme/host/core.c-1031-\tif (op == nvme_cmd_write \u0026\u0026 ns-\u003ehead-\u003enr_plids) {\ndrivers/nvme/host/core.c:1032:\t\tu16 write_stream = req-\u003ebio-\u003ebi_write_stream;\ndrivers/nvme/host/core.c-1033-\ndrivers/nvme/host/core.c:1034:\t\tif (WARN_ON_ONCE(write_stream \u003e ns-\u003ehead-\u003enr_plids))\ndrivers/nvme/host/core.c-1035-\t\t\treturn BLK_STS_INVAL;\ndrivers/nvme/host/core.c-1036-\ndrivers/nvme/host/core.c:1037:\t\tif (write_stream) {\ndrivers/nvme/host/core.c:1038:\t\t\tdsmgmt \|= ns-\u003ehead-\u003eplids[write_stream - 1] \u003c\u003c 16;\ndrivers/nvme/host/core.c-1039-\t\t\tcontrol \|= NVME_RW_DTYPE_DPLCMT;\n--\ndrivers/nvme/host/core.c=2332=static int nvme_query_fdp_info(struct nvme_ns ns, struct nvme_ns_info info)\n--\ndrivers/nvme/host/core.c-2386-\t\thead-\u003eplids[i] = le16_to_cpu(ruhs-\u003eruhsd[i].pid);\ndrivers/nvme/host/core.c:2387:\thead-\u003ewrite_stream_granularity = min(info-\u003eruns, U32_MAX);\ndrivers/nvme/host/core.c-2388-free:\n--\ndrivers/nvme/host/core.c=2398=static int nvme_update_ns_info_block(struct nvme_ns ns,\n--\ndrivers/nvme/host/core.c-2492-\ndrivers/nvme/host/core.c:2493:\tlim.max_write_streams = ns-\u003ehead-\u003enr_plids;\ndrivers/nvme/host/core.c:2494:\tlim.write_stream_granularity = ns-\u003ehead-\u003ewrite_stream_granularity;\ndrivers/nvme/host/core.c-2495-\n--\ndrivers/nvme/host/core.c=2539=static int nvme_update_ns_info(struct nvme_ns ns, struct nvme_ns_info info)\n--\ndrivers/nvme/host/core.c-2610-\t\t\tnvme_init_integrity(ns-\u003ehead, \u0026lim, info);\ndrivers/nvme/host/core.c:2611:\t\tlim.max_write_streams = ns_lim-\u003emax_write_streams;\ndrivers/nvme/host/core.c:2612:\t\tlim.write_stream_granularity = ns_lim-\u003ewrite_stream_granularity;\ndrivers/nvme/host/core.c-2613-\t\tret = queue_limits_commit_update(ns-\u003ehead-\u003edisk-\u003equeue, \u0026lim);\n--\ndrivers/nvme/host/nvme.h=542=struct nvme_ns_head {\n--\ndrivers/nvme/host/nvme.h-574-\tu16\t\t\tplids;\ndrivers/nvme/host/nvme.h:575:\tu32\t\t\twrite_stream_granularity;\ndrivers/nvme/host/nvme.h-576-#ifdef CONFIG_NVME_MULTIPATH\n--\ndrivers/scsi/smartpqi/smartpqi.h=1109=struct pqi_raid_io_stats {\ndrivers/scsi/smartpqi/smartpqi.h-1110-\tu64\traid_bypass_cnt;\ndrivers/scsi/smartpqi/smartpqi.h:1111:\tu64\twrite_stream_cnt;\ndrivers/scsi/smartpqi/smartpqi.h-1112-};\n--\ndrivers/scsi/smartpqi/smartpqi_init.c=5962=void pqi_prep_for_scsi_done(struct scsi_cmnd scmd)\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-5995-\ndrivers/scsi/smartpqi/smartpqi_init.c:5996:static bool pqi_is_parity_write_stream(struct pqi_ctrl_info ctrl_info,\ndrivers/scsi/smartpqi/smartpqi_init.c-5997-\tstruct scsi_cmnd scmd)\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-6046-\t\t\tpqi_stream_data-\u003elast_accessed = jiffies;\ndrivers/scsi/smartpqi/smartpqi_init.c:6047:\t\t\tper_cpu_ptr(device-\u003eraid_io_stats, raw_smp_processor_id())-\u003ewrite_stream_cnt++;\ndrivers/scsi/smartpqi/smartpqi_init.c-6048-\t\t\treturn true;\n--\ndrivers/scsi/smartpqi/smartpqi_init.c=6072=static enum scsi_qc_status pqi_scsi_queue_command(struct Scsi_Host shost,\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-6122-\t\t\tpqi_is_bypass_eligible_request(scmd) \u0026\u0026\ndrivers/scsi/smartpqi/smartpqi_init.c:6123:\t\t\t!pqi_is_parity_write_stream(ctrl_info, scmd)) {\ndrivers/scsi/smartpqi/smartpqi_init.c-6124-\t\t\trc = pqi_raid_bypass_submit_scsi_cmd(ctrl_info, device, scmd, queue_group);\n--\ndrivers/scsi/smartpqi/smartpqi_init.c=7681=static ssize_t pqi_numa_node_show(struct device dev,\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-7692-\ndrivers/scsi/smartpqi/smartpqi_init.c:7693:static ssize_t pqi_write_stream_cnt_show(struct device dev,\ndrivers/scsi/smartpqi/smartpqi_init.c-7694-\tstruct device_attribute attr, char buffer)\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-7699-\tunsigned long flags;\ndrivers/scsi/smartpqi/smartpqi_init.c:7700:\tu64 write_stream_cnt;\ndrivers/scsi/smartpqi/smartpqi_init.c-7701-\tint cpu;\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-7716-\ndrivers/scsi/smartpqi/smartpqi_init.c:7717:\twrite_stream_cnt = 0;\ndrivers/scsi/smartpqi/smartpqi_init.c-7718-\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-7720-\t\tfor_each_online_cpu(cpu) {\ndrivers/scsi/smartpqi/smartpqi_init.c:7721:\t\t\twrite_stream_cnt += per_cpu_ptr(device-\u003eraid_io_stats, cpu)-\u003ewrite_stream_cnt;\ndrivers/scsi/smartpqi/smartpqi_init.c-7722-\t\t}\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-7726-\ndrivers/scsi/smartpqi/smartpqi_init.c:7727:\treturn scnprintf(buffer, PAGE_SIZE, \"0x%llx\\n\", write_stream_cnt);\ndrivers/scsi/smartpqi/smartpqi_init.c-7728-}\n--\ndrivers/scsi/smartpqi/smartpqi_init.c=7739=static DEVICE_ATTR(numa_node, 0444, pqi_numa_node_show, NULL);\ndrivers/scsi/smartpqi/smartpqi_init.c:7740:static DEVICE_ATTR(write_stream_cnt, 0444, pqi_write_stream_cnt_show, NULL);\ndrivers/scsi/smartpqi/smartpqi_init.c-7741-\ndrivers/scsi/smartpqi/smartpqi_init.c=7742=static struct attribute pqi_sdev_attrs[] = {\n--\ndrivers/scsi/smartpqi/smartpqi_init.c-7751-\t\u0026dev_attr_numa_node.attr,\ndrivers/scsi/smartpqi/smartpqi_init.c:7752:\t\u0026dev_attr_write_stream_cnt.attr,\ndrivers/scsi/smartpqi/smartpqi_init.c-7753-\tNULL\n--\ndrivers/usb/gadget/udc/tegra-xudc.c=1083=static void tegra_xudc_queue_one_trb(struct tegra_xudc_ep ep,\n--\ndrivers/usb/gadget/udc/tegra-xudc.c-1137-\t\ttrb_write_type(trb, TRB_TYPE_STREAM);\ndrivers/usb/gadget/udc/tegra-xudc.c:1138:\t\ttrb_write_stream_id(trb, req-\u003eusb_req.stream_id);\ndrivers/usb/gadget/udc/tegra-xudc.c-1139-\t} else {\ndrivers/usb/gadget/udc/tegra-xudc.c-1140-\t\ttrb_write_type(trb, TRB_TYPE_NORMAL);\ndrivers/usb/gadget/udc/tegra-xudc.c:1141:\t\ttrb_write_stream_id(trb, 0);\ndrivers/usb/gadget/udc/tegra-xudc.c-1142-\t}\n--\nfs/Makefile=25=obj-$(CONFIG_EPOLL)\t\t+= eventpoll.o\nfs/Makefile:26:obj-y\t\t\t\t+= anon_inodes.o write_streams.o\nfs/Makefile-27-obj-$(CONFIG_SIGNALFD)\t\t+= signalfd.o\n--\nfs/aio.c=1563=static int aio_prep_rw(struct kiocb req, const struct iocb iocb, int rw_type)\n--\nfs/aio.c-1566-\nfs/aio.c:1567:\treq-\u003eki_write_stream = 0;\nfs/aio.c-1568-\treq-\u003eki_complete = aio_complete_rw;\n--\nfs/f2fs/data.c=495=static struct bio __bio_alloc(struct f2fs_io_info fio, int npages)\n--\nfs/f2fs/data.c-514-\t\t\t\t\t\tfio-\u003etype, fio-\u003etemp);\nfs/f2fs/data.c:515:\t\tbio-\u003ebi_write_stream = f2fs_io_type_to_write_stream(bdev, fio-\u003etype,\nfs/f2fs/data.c-516-\t\t\t\t\t\t\t\t fio-\u003etemp);\n--\nfs/f2fs/f2fs.h=4133=enum rw_hint f2fs_io_type_to_rw_hint(struct f2fs_sb_info sbi,\nfs/f2fs/f2fs.h-4134-\t\t\tenum page_type type, enum temp_type temp);\nfs/f2fs/f2fs.h:4135:u8 f2fs_io_type_to_write_stream(struct block_device bdev,\nfs/f2fs/f2fs.h-4136-\t\t\t\tenum page_type type, enum temp_type temp);\n--\nfs/f2fs/file.c=5451=static int f2fs_dio_write_end_io(struct kiocb iocb, ssize_t size, int error,\n--\nfs/f2fs/file.c-5463-\nfs/f2fs/file.c:5464:static bool f2fs_valid_write_stream(struct f2fs_sb_info sbi, u8 write_stream)\nfs/f2fs/file.c-5465-{\n--\nfs/f2fs/file.c-5467-\nfs/f2fs/file.c:5468:\tif (!write_stream)\nfs/f2fs/file.c-5469-\t\treturn true;\nfs/f2fs/file.c-5470-\tif (!f2fs_is_multi_device(sbi))\nfs/f2fs/file.c:5471:\t\treturn write_stream \u003c= bdev_max_write_streams(sbi-\u003esb-\u003es_bdev);\nfs/f2fs/file.c-5472-\nfs/f2fs/file.c-5473-\tfor (i = 0; i \u003c sbi-\u003es_ndevs; i++)\nfs/f2fs/file.c:5474:\t\tif (write_stream \u003e bdev_max_write_streams(FDEV(i).bdev))\nfs/f2fs/file.c-5475-\t\t\treturn false;\n--\nfs/f2fs/file.c=5479=static void f2fs_dio_write_submit_io(const struct iomap_iter iter,\n--\nfs/f2fs/file.c-5488-\tbio-\u003ebi_write_hint = f2fs_io_type_to_rw_hint(sbi, DATA, temp);\nfs/f2fs/file.c:5489:\tbio-\u003ebi_write_stream =\nfs/f2fs/file.c:5490:\t\tiocb-\u003eki_write_stream ? iocb-\u003eki_write_stream :\nfs/f2fs/file.c:5491:\t\tf2fs_io_type_to_write_stream(bio-\u003ebi_bdev, DATA, temp);\nfs/f2fs/file.c-5492-\tf2fs_dio_iostat_start(sbi, bio);\n--\nfs/f2fs/file.c=5514=static ssize_t f2fs_dio_write_iter(struct kiocb iocb, struct iov_iter from,\n--\nfs/f2fs/file.c-5529-\nfs/f2fs/file.c:5530:\tif (!f2fs_valid_write_stream(sbi, iocb-\u003eki_write_stream)) {\nfs/f2fs/file.c-5531-\t\tret = -EINVAL;\n--\nfs/f2fs/segment.c=3709=enum rw_hint f2fs_io_type_to_rw_hint(struct f2fs_sb_info sbi,\n--\nfs/f2fs/segment.c-3741-\nfs/f2fs/segment.c:3742:u8 f2fs_io_type_to_write_stream(struct block_device bdev,\nfs/f2fs/segment.c-3743-\t\t\t\tenum page_type type, enum temp_type temp)\nfs/f2fs/segment.c-3744-{\nfs/f2fs/segment.c:3745:\tunsigned short nr = bdev_max_write_streams(bdev);\nfs/f2fs/segment.c-3746-\n--\nfs/fcntl.c=369=static long fcntl_set_rw_hint(struct file file, unsigned long arg)\n--\nfs/fcntl.c-384-\tspin_lock(\u0026inode-\u003ei_lock);\nfs/fcntl.c:385:\tif (hint != WRITE_LIFE_NOT_SET \u0026\u0026 READ_ONCE(inode-\u003ei_write_stream)) {\nfs/fcntl.c-386-\t\tspin_unlock(\u0026inode-\u003ei_lock);\n--\nfs/inode.c=223=int inode_init_always_gfp(struct super_block sb, struct inode inode, gfp_t gfp)\n--\nfs/inode.c-248-\tinode-\u003ei_write_hint = WRITE_LIFE_NOT_SET;\nfs/inode.c:249:\tinode-\u003ei_write_stream = 0;\nfs/inode.c-250-\tinode-\u003ei_blocks = 0;\n--\nfs/iomap/direct-io.c=335=static ssize_t iomap_dio_bio_iter_one(struct iomap_iter iter,\n--\nfs/iomap/direct-io.c-351-\tbio-\u003ebi_write_hint = iter-\u003einode-\u003ei_write_hint;\nfs/iomap/direct-io.c:352:\tbio-\u003ebi_write_stream = iter-\u003eiomap.write_stream;\nfs/iomap/direct-io.c-353-\tbio-\u003ebi_ioprio = dio-\u003eiocb-\u003eki_ioprio;\n--\nfs/iomap/ioend.c=159=static struct iomap_ioend iomap_alloc_ioend(struct iomap_writepage_ctx wpc,\n--\nfs/iomap/ioend.c-168-\tbio-\u003ebi_write_hint = wpc-\u003einode-\u003ei_write_hint;\nfs/iomap/ioend.c:169:\tbio-\u003ebi_write_stream = wpc-\u003eiomap.write_stream;\nfs/iomap/ioend.c-170-\twbc_init_bio(wpc-\u003ewbc, bio);\n--\nfs/iomap/ioend.c=175=static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx wpc, loff_t pos,\n--\nfs/iomap/ioend.c-192-\t\treturn false;\nfs/iomap/ioend.c:193:\tif (wpc-\u003eiomap.write_stream != ioend-\u003eio_bio.bi_write_stream)\nfs/iomap/ioend.c-194-\t\treturn false;\n--\nfs/netfs/write_retry.c-16- /\nfs/netfs/write_retry.c:17:static void netfs_retry_write_stream(struct netfs_io_request wreq,\nfs/netfs/write_retry.c-18-\t\t\t\t struct netfs_io_stream stream)\n--\nfs/netfs/write_retry.c=208=void netfs_retry_writes(struct netfs_io_request wreq)\n--\nfs/netfs/write_retry.c-234-\t\t\tstream-\u003eneed_retry = false;\nfs/netfs/write_retry.c:235:\t\t\tnetfs_retry_write_stream(wreq, stream);\nfs/netfs/write_retry.c-236-\t\t}\n--\nfs/write_streams.c-9-#include \u003clinux/slab.h\u003e\nfs/write_streams.c:10:#include \u003clinux/write_streams.h\u003e\nfs/write_streams.c-11-\nfs/write_streams.c:12:struct write_stream {\nfs/write_streams.c:13:\tstruct write_stream_pool\tpool;\nfs/write_streams.c-14-\tstruct vfsmount\t\t\tmnt;\t/ pins the mount /\n--\nfs/write_streams.c-17-\nfs/write_streams.c:18:static int write_stream_release(struct inode inode, struct file file)\nfs/write_streams.c-19-{\nfs/write_streams.c:20:\tstruct write_stream ws = file-\u003eprivate_data;\nfs/write_streams.c-21-\n--\nfs/write_streams.c-29-\nfs/write_streams.c:30:static const struct file_operations write_stream_fops = {\nfs/write_streams.c:31:\t.release\t= write_stream_release,\nfs/write_streams.c-32-\t.llseek\t\t= noop_llseek,\n--\nfs/write_streams.c-35-/*\nfs/write_streams.c:36: write_stream_pool_init - size a write stream pool\nfs/write_streams.c-37- * @pool: pool to initialise\n--\nfs/write_streams.c-41- /\nfs/write_streams.c:42:int write_stream_pool_init(struct write_stream_pool pool, unsigned int nr)\nfs/write_streams.c-43-{\n--\nfs/write_streams.c-56-}\nfs/write_streams.c:57:EXPORT_SYMBOL_GPL(write_stream_pool_init);\nfs/write_streams.c-58-\nfs/write_streams.c-59-/*\nfs/write_streams.c:60: write_stream_pool_destroy - free a write stream pool\nfs/write_streams.c-61- * @pool: pool to release\nfs/write_streams.c-62- /\nfs/write_streams.c:63:void write_stream_pool_destroy(struct write_stream_pool pool)\nfs/write_streams.c-64-{\n--\nfs/write_streams.c-68-}\nfs/write_streams.c:69:EXPORT_SYMBOL_GPL(write_stream_pool_destroy);\nfs/write_streams.c-70-\nfs/write_streams.c-71-/*\nfs/write_streams.c:72: write_stream_alloc_fd - reserve a slot and return an fd naming it\nfs/write_streams.c-73- * @pool: pool to reserve from\n--\nfs/write_streams.c-78- /\nfs/write_streams.c:79:int write_stream_alloc_fd(struct write_stream_pool pool, struct file file)\nfs/write_streams.c-80-{\nfs/write_streams.c:81:\tstruct write_stream ws;\nfs/write_streams.c-82-\tunsigned int slot;\n--\nfs/write_streams.c-105-\nfs/write_streams.c:106:\tfd = anon_inode_getfd(\"[write_stream]\", \u0026write_stream_fops, ws,\nfs/write_streams.c-107-\t\t\t O_RDONLY \| O_CLOEXEC);\n--\nfs/write_streams.c-116-}\nfs/write_streams.c:117:EXPORT_SYMBOL_GPL(write_stream_alloc_fd);\nfs/write_streams.c-118-\nfs/write_streams.c-119-/*\nfs/write_streams.c:120: write_stream_get_id - the id a stream file names\nfs/write_streams.c-121- * @file: candidate stream file\n--\nfs/write_streams.c-126- /\nfs/write_streams.c:127:int write_stream_get_id(struct file file, const struct write_stream_pool pool)\nfs/write_streams.c-128-{\nfs/write_streams.c:129:\tstruct write_stream ws;\nfs/write_streams.c-130-\nfs/write_streams.c:131:\tif (file-\u003ef_op != \u0026write_stream_fops)\nfs/write_streams.c-132-\t\treturn -EINVAL;\n--\nfs/write_streams.c-137-}\nfs/write_streams.c:138:EXPORT_SYMBOL_GPL(write_stream_get_id);\n--\nfs/xfs/libxfs/xfs_bmap.c=3582=static xfs_agnumber_t\nfs/xfs/libxfs/xfs_bmap.c:3583:xfs_bmap_write_stream_agno(\nfs/xfs/libxfs/xfs_bmap.c-3584-\tstruct xfs_inode\tip,\n--\nfs/xfs/libxfs/xfs_bmap.c-3589-\tunsigned int\t\tnr_streams =\nfs/xfs/libxfs/xfs_bmap.c:3590:\t\twrite_stream_pool_count(\u0026mp-\u003em_ddev_targp-\u003ebt_stream_pool);\nfs/xfs/libxfs/xfs_bmap.c-3591-\txfs_agnumber_t\t\tag_set_size, start_agno;\n--\nfs/xfs/libxfs/xfs_bmap.c=3647=static int\nfs/xfs/libxfs/xfs_bmap.c:3648:xfs_bmap_btalloc_write_stream(\nfs/xfs/libxfs/xfs_bmap.c-3649-\tstruct xfs_bmalloca\tap,\n--\nfs/xfs/libxfs/xfs_bmap.c-3656-\nfs/xfs/libxfs/xfs_bmap.c:3657:\tagno = xfs_bmap_write_stream_agno(ap-\u003eip, stream_id);\nfs/xfs/libxfs/xfs_bmap.c-3658-\tap-\u003eblkno = XFS_AGB_TO_FSB(mp, agno, 0);\n--\nfs/xfs/libxfs/xfs_bmap.c=3673=xfs_bmap_btalloc(\n--\nfs/xfs/libxfs/xfs_bmap.c-3703-\nfs/xfs/libxfs/xfs_bmap.c:3704:\tstream_id = READ_ONCE(VFS_I(ap-\u003eip)-\u003ei_write_stream);\nfs/xfs/libxfs/xfs_bmap.c-3705-\n--\nfs/xfs/libxfs/xfs_bmap.c-3711-\telse if ((ap-\u003edatatype \u0026 XFS_ALLOC_USERDATA) \u0026\u0026 stream_id)\nfs/xfs/libxfs/xfs_bmap.c:3712:\t\terror = xfs_bmap_btalloc_write_stream(ap, \u0026args, stripe_align,\nfs/xfs/libxfs/xfs_bmap.c-3713-\t\t\t\tstream_id);\n--\nfs/xfs/xfs_buf.c=1647=xfs_free_buftarg(\n--\nfs/xfs/xfs_buf.c-1649-{\nfs/xfs/xfs_buf.c:1650:\twrite_stream_pool_destroy(\u0026btp-\u003ebt_stream_pool);\nfs/xfs/xfs_buf.c-1651-\txfs_destroy_buftarg(btp);\n--\nfs/xfs/xfs_buf.c=1691=static unsigned int\nfs/xfs/xfs_buf.c:1692:xfs_sw_write_stream_count(\nfs/xfs/xfs_buf.c-1693-\tunsigned int\t\tnr_groups)\n--\nfs/xfs/xfs_buf.c=1707=xfs_buftarg_init_streams(\n--\nfs/xfs/xfs_buf.c-1713-\nfs/xfs/xfs_buf.c:1714:\thw_streams = bdev_max_write_streams(btp-\u003ebt_bdev);\nfs/xfs/xfs_buf.c-1715-\tif (hw_streams)\n--\nfs/xfs/xfs_buf.c-1717-\telse\nfs/xfs/xfs_buf.c:1718:\t\tnr_streams = xfs_sw_write_stream_count(nr_groups);\nfs/xfs/xfs_buf.c:1719:\treturn write_stream_pool_init(\u0026btp-\u003ebt_stream_pool, nr_streams);\nfs/xfs/xfs_buf.c-1720-}\n--\nfs/xfs/xfs_buf.h-17-#include \u003clinux/lockref.h\u003e\nfs/xfs/xfs_buf.h:18:#include \u003clinux/write_streams.h\u003e\nfs/xfs/xfs_buf.h-19-\n--\nfs/xfs/xfs_buf.h=82=struct xfs_buftarg {\n--\nfs/xfs/xfs_buf.h-106-\t/* slot pool for stream fds on this device /\nfs/xfs/xfs_buf.h:107:\tstruct write_stream_pool bt_stream_pool;\nfs/xfs/xfs_buf.h-108-\n--\nfs/xfs/xfs_inode.c-6-#include \u003clinux/iversion.h\u003e\nfs/xfs/xfs_inode.c:7:#include \u003clinux/write_streams.h\u003e\nfs/xfs/xfs_inode.c-8-\n--\nfs/xfs/xfs_inode.c=52=int\nfs/xfs/xfs_inode.c:53:xfs_inode_max_write_streams(\nfs/xfs/xfs_inode.c-54-\tstruct xfs_inode\tip)\n--\nfs/xfs/xfs_inode.c-61-\t\treturn 0;\nfs/xfs/xfs_inode.c:62:\treturn write_stream_pool_count(\u0026xfs_inode_buftarg(ip)-\u003ebt_stream_pool);\nfs/xfs/xfs_inode.c-63-}\n--\nfs/xfs/xfs_inode.c=66=int\nfs/xfs/xfs_inode.c:67:xfs_inode_set_write_stream(\nfs/xfs/xfs_inode.c-68-\tstruct xfs_inode\tip,\n--\nfs/xfs/xfs_inode.c-83-\ttarget = xfs_inode_buftarg(ip);\nfs/xfs/xfs_inode.c:84:\tid = write_stream_get_id(fd_file(f), \u0026target-\u003ebt_stream_pool);\nfs/xfs/xfs_inode.c-85-\tif (id \u003c 0) {\n--\nfs/xfs/xfs_inode.c-102-\t}\nfs/xfs/xfs_inode.c:103:\tWRITE_ONCE(VFS_I(ip)-\u003ei_write_stream, id);\nfs/xfs/xfs_inode.c-104-\tspin_unlock(\u0026VFS_I(ip)-\u003ei_lock);\n--\nfs/xfs/xfs_inode.c=110=void\nfs/xfs/xfs_inode.c:111:xfs_inode_clear_write_stream(\nfs/xfs/xfs_inode.c-112-\tstruct xfs_inode\tip)\n--\nfs/xfs/xfs_inode.c-114-\txfs_ilock(ip, XFS_ILOCK_EXCL);\nfs/xfs/xfs_inode.c:115:\tWRITE_ONCE(VFS_I(ip)-\u003ei_write_stream, 0);\nfs/xfs/xfs_inode.c-116-\txfs_iunlock(ip, XFS_ILOCK_EXCL);\n--\nfs/xfs/xfs_inode.h=671=int xfs_icreate_dqalloc(const struct xfs_icreate_args args,\n--\nfs/xfs/xfs_inode.h-674-\nfs/xfs/xfs_inode.h:675:int xfs_inode_max_write_streams(struct xfs_inode ip);\n\n" }
29/3	2026/09/23 06:46	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 26656 output: 27 thoughts: 223 Thoughts: Analyzing the `struct iomap` Initialization and Usage Okay, let's dive into this `struct iomap`. My initial thought is to figure out the scope of its usage within the kernel. I need to understand if there are other areas, besides the immediate context, where `struct iomap` is initialized or employed. A wider view will help me anticipate any potential interactions or dependencies. Now, let's take a closer look at the members themselves: the `offset`, `length`, `type`, the flags, all the way down to `validity_cookie` . I'm particularly interested in how these are populated. A quick check reveals it contains: `offset`, `length`, `type`, `flags`, `write_stream`, `bdev`, `dax_dev`, `inline_data`, `folio_ops`, and `validity_cookie`. A fundamental question arises: is this structure zeroed out upon creation? Understanding the initial state of the structure is crucial to avoiding potential issues later. If it's not explicitly zeroed, then any uninitialized memory could lead to subtle, hard-to-debug problems. To get a clearer picture of how `struct iomap` comes to life, I'll need to see how filesystems initialize it. Let's trace the initialization paths; it's also worth checking how `iomap_iter` handles it. I should grep the codebase to find usages of `iomap_iter` or instances where `struct iomap` is explicitly cleared to get a better overview of its lifecycle.
30/3	2026/09/23 06:46	tool	grepper	0m Args: { "Expression": "memset.iomap", "PathPrefix": "fs/" } Results:* { "Output": "fs/gfs2/bmap.c=2508=static ssize_t gfs2_writeback_range(struct iomap_writepage_ctx wpc,\n--\nfs/gfs2/bmap.c-2517-\nfs/gfs2/bmap.c:2518:\t\tmemset(\u0026wpc-\u003eiomap, 0, sizeof(wpc-\u003eiomap));\nfs/gfs2/bmap.c-2519-\t\tret = gfs2_iomap_get(wpc-\u003einode, offset, INT_MAX, \u0026wpc-\u003eiomap);\n--\nfs/iomap/direct-io.c=607=static int iomap_dio_inline_iter(struct iomap_iter iomi, struct iomap_dio dio)\n--\nfs/iomap/direct-io.c-622-\t\tif (pos \u003e size)\nfs/iomap/direct-io.c:623:\t\t\tmemset(iomap_inline_data(iomap, size), 0, pos - size);\nfs/iomap/direct-io.c-624-\t\tcopied = copy_from_iter(inline_data, length, iter);\n--\nfs/iomap/iter.c=63=int iomap_iter_continue(const struct iomap_iter iter, struct iomap iomap,\n--\nfs/iomap/iter.c-92-\nfs/iomap/iter.c:93:\tmemset(iomap, 0, sizeof(iomap));\nfs/iomap/iter.c-94-\tmemset(srcmap, 0, sizeof(*srcmap));\n" }
31/3	2026/09/23 06:46	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 27672 output: 36 thoughts: 62 Thoughts: Here's my summary, as if I were thinking it: Inspecting the IOMap Iterator Initialization Right, so I'm looking into how the iomap iterator works, and I see that both `iomap_iter_continue` and, implicitly, `iomap_iter` itself perform a `memset` on the `iomap` structure. Okay, that's interesting. It's initializing the `iomap` struct to zero before use. Probably for safety and to ensure predictable behavior, especially if the `iomap` struct contains padding or other uninitialized fields that could influence the iteration process if left untouched. I'll take a closer look at `fs/iomap/iter.c`, specifically around lines 63 through 100, to understand the context and rationale behind this initialization. Need to see what fields are being set up or cleared. It's likely a critical piece in handling edge cases or ensuring the iterator starts from a known, consistent state.
32/3	2026/09/23 06:46	tool	read-file	0m Args: { "File": "fs/iomap/iter.c", "FirstLine": 1, "LineCount": 100 } Results: { "Contents": " 1:\t// SPDX-License-Identifier: GPL-2.0\n 2:\t/\n 3:\t Copyright (C) 2010 Red Hat, Inc.\n 4:\t * Copyright (c) 2016-2021 Christoph Hellwig.\n 5:\t /\n 6:\t#include \u003clinux/iomap.h\u003e\n 7:\t#include \"trace.h\"\n 8:\t\n 9:\t/\n 10:\t * Release the iter folio batch. Note that the iomap flag is meant to control\n 11:\t * the I/O path for the mapping and may not be set in error situations.\n 12:\t /\n 13:\tstatic inline void iomap_iter_clean_fbatch(const struct iomap_iter iter,\n 14:\t\t\tstruct iomap iomap)\n 15:\t{\n 16:\t\tif (!iter-\u003efbatch)\n 17:\t\t\treturn;\n 18:\t\tiomap-\u003eflags \u0026= ~IOMAP_F_FOLIO_BATCH;\n 19:\t\tif (folio_batch_count(iter-\u003efbatch)) {\n 20:\t\t\tfolio_batch_release(iter-\u003efbatch);\n 21:\t\t\tfolio_batch_reinit(iter-\u003efbatch);\n 22:\t\t}\n 23:\t}\n 24:\t\n 25:\t/ Advance the current iterator position and decrement the remaining length /\n 26:\tint iomap_iter_advance(struct iomap_iter iter, u64 count)\n 27:\t{\n 28:\t\tif (WARN_ON_ONCE(count \u003e iomap_length(iter)))\n 29:\t\t\treturn -EIO;\n 30:\t\titer-\u003epos += count;\n 31:\t\titer-\u003elen -= count;\n 32:\t\treturn 0;\n 33:\t}\n 34:\t\n 35:\tstatic inline void iomap_iter_done(struct iomap_iter iter)\n 36:\t{\n 37:\t\tWARN_ON_ONCE(iter-\u003eiomap.offset \u003e iter-\u003epos);\n 38:\t\tWARN_ON_ONCE(iter-\u003eiomap.length == 0);\n 39:\t\tWARN_ON_ONCE(iter-\u003eiomap.offset + iter-\u003eiomap.length \u003c= iter-\u003epos);\n 40:\t\tWARN_ON_ONCE(iter-\u003eiomap.flags \u0026 IOMAP_F_STALE);\n 41:\t\n 42:\t\titer-\u003eiter_start_pos = iter-\u003epos;\n 43:\t\n 44:\t\ttrace_iomap_iter_dstmap(iter-\u003einode, \u0026iter-\u003eiomap);\n 45:\t\tif (iter-\u003esrcmap.type != IOMAP_HOLE)\n 46:\t\t\ttrace_iomap_iter_srcmap(iter-\u003einode, \u0026iter-\u003esrcmap);\n 47:\t}\n 48:\t\n 49:\t/\n 50:\t iomap_iter_continue - decide whether iteration should continue\n 51:\t * @iter: iteration structure\n 52:\t * @iomap: the mapping that was just processed\n 53:\t * @srcmap: the source mapping that was just processed\n 54:\t \n 55:\t Helper normally called via iomap_iter_next(). Called after the previous\n 56:\t * mapping has been finished to determine whether there is more of the file\n 57:\t * range left to process.\n 58:\t \n 59:\t Returns 1 if there is more work to do, in which case @iomap and @srcmap are\n 60:\t * cleared so the caller can produce the next mapping; zero if the range is\n 61:\t * fully consumed; or a negative errno on error.\n 62:\t /\n 63:\tint iomap_iter_continue(const struct iomap_iter iter, struct iomap iomap,\n 64:\t\t\tstruct iomap srcmap, int ret)\n 65:\t{\n 66:\t\tconst bool stale = iomap-\u003eflags \u0026 IOMAP_F_STALE;\n 67:\t\tconst ssize_t advanced = iter-\u003epos - iter-\u003eiter_start_pos;\n 68:\t\n 69:\t\tif (ret \u003c 0 \u0026\u0026 !advanced)\n 70:\t\t\treturn ret;\n 71:\t\n 72:\t\t/\n 73:\t\t Use iter-\u003elen to determine whether to continue onto the next mapping.\n 74:\t\t * Explicitly terminate on error status or if the current iter has not\n 75:\t\t * advanced at all (i.e. no work was done for some reason) unless the\n 76:\t\t * mapping has been marked stale and needs to be reprocessed.\n 77:\t\t /\n 78:\t\tif (WARN_ON_ONCE(iter-\u003estatus \u003e 0))\n 79:\t\t\t/ detect old return semantics where this would advance /\n 80:\t\t\tret = -EIO;\n 81:\t\telse if (iter-\u003estatus \u003c 0)\n 82:\t\t\tret = iter-\u003estatus;\n 83:\t\telse if (iter-\u003elen == 0 \|\| (!advanced \u0026\u0026 !stale))\n 84:\t\t\tret = 0;\n 85:\t\telse\n 86:\t\t\tret = 1;\n 87:\t\n 88:\t\tiomap_iter_clean_fbatch(iter, iomap);\n 89:\t\n 90:\t\tif (ret \u003c= 0)\n 91:\t\t\treturn ret;\n 92:\t\n 93:\t\tmemset(iomap, 0, sizeof(iomap));\n 94:\t\tmemset(srcmap, 0, sizeof(srcmap));\n 95:\t\n 96:\t\treturn ret;\n 97:\t}\n 98:\tEXPORT_SYMBOL_GPL(iomap_iter_continue);\n 99:\t\n 100:\t/*\n" }
33/3	2026/09/23 06:46	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 29493 output: 37 thoughts: 40 Thoughts: Here's a summary of my thought process, as requested: Diving into `iomap_iter` Initialization Okay, time to get my hands dirty. I need to understand how the `iomap_iter` is initialized. My immediate plan is to zero in on the relevant code, so I'm going to start by examining lines 101 through 160 of `fs/iomap/iter.c`. That should give me the core logic surrounding the initialization process. Let's see what interesting details I can extract.
34/3	2026/09/23 06:47	tool	read-file	0m Args: { "File": "fs/iomap/iter.c", "FirstLine": 101, "LineCount": 60 } Results: { "Contents": " 101:\t * iomap_iter - iterate over ranges in a file\n 102:\t * @iter: iteration structure\n 103:\t * @ops: iomap ops provided by the filesystem\n 104:\t \n 105:\t Iterate over filesystem-provided space mappings for the provided file range.\n 106:\t \n 107:\t This function handles cleanup of resources acquired for iteration when the\n 108:\t * filesystem indicates there are no more space mappings, which means that this\n 109:\t * function must be called in a loop that continues as long it returns a\n 110:\t * positive value. If 0 or a negative value is returned, the caller must not\n 111:\t * return to the loop body. Within a loop body, there are two ways to break out\n 112:\t * of the loop body: leave @iter.status unchanged, or set it to a negative\n 113:\t * errno.\n 114:\t /\n 115:\tint iomap_iter(struct iomap_iter iter, const struct iomap_ops *ops)\n 116:\t{\n 117:\t\tint ret;\n 118:\t\n 119:\t\ttrace_iomap_iter(iter, ops, _RET_IP_);\n 120:\t\n 121:\t\tif (ops-\u003eiomap_next)\n 122:\t\t\tret = ops-\u003eiomap_next(iter, \u0026iter-\u003eiomap, \u0026iter-\u003esrcmap);\n 123:\t\telse\n 124:\t\t\tret = iomap_iter_next(iter, \u0026iter-\u003eiomap, \u0026iter-\u003esrcmap,\n 125:\t\t\t\t\tops-\u003eiomap_begin, ops-\u003eiomap_end);\n 126:\t\n 127:\t\titer-\u003estatus = 0;\n 128:\t\tif (ret \u003e 0)\n 129:\t\t\tiomap_iter_done(iter);\n 130:\t\telse if (ret \u003c 0)\n 131:\t\t\tiomap_iter_clean_fbatch(iter, \u0026iter-\u003eiomap);\n 132:\t\n 133:\t\treturn ret;\n 134:\t}\n" }
35/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30272 output: 21 thoughts: 75 Thoughts: Okay, let's break this down. Diving into `iomap_iter_next` and Its Context Right, so I need to understand how `iomap_iter_next` functions. First instinct: where's the definition? Let's check the area around lines 50-65, or perhaps even earlier in the file, just to get a lay of the land. I need to see how it's defined in relation to its neighbors. Hang on a second… before I can understand `iomap_iter_next`, I need to know where this whole `iomap_iter` structure is coming from and how it's initialized. I need to trace back from `iomap_iter_next` to `iomap_iter_init`. Or, maybe it's not `iomap_iter_init`. The point is, how is `struct iomap_iter` created in the first place? It's all about context. Okay, let's skip the manual search for now; this is a complex project and I can't keep track of everything. The quickest way to understand the whole struct, its declaration and how it's used is to `grep` for the declaration of `struct iomap_iter`. That should give me a good overview of how this struct is defined and where it lives within the project's code base.
36/3	2026/09/23 06:47	tool	grepper	0m Args: { "Expression": "struct iomap_iter \\{" } Results: { "Output": "include/linux/iomap.h=243=struct iomap_ops {\n--\ninclude/linux/iomap.h-263- /\ninclude/linux/iomap.h:264:struct iomap_iter {\ninclude/linux/iomap.h-265-\tstruct inode inode;\n" }
37/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 30766 output: 30 thoughts: 44 Thoughts: Here's my thought process, summarized as you requested: Investigating `iomap_iter` Initialization Okay, so I need to understand how callers are initializing the `struct iomap_iter`. I'm going to start with a grep to find instances where it's being declared and potentially initialized. I'll focus my search within the `fs/iomap/` and `fs/` directories, since that's where I'd expect to find code directly related to I/O mapping and file systems in general. The specific pattern I'm looking for is `struct iomap_iter iter =` – the declaration and (likely) initialization of the `iter` variable. Hopefully, this will lead me to the key usages and patterns. Time to start the search and see what pops up!
38/3	2026/09/23 06:47	tool	grepper	0m Args: { "Expression": "struct iomap_iter iter =", "PathPrefix": "fs/" } Results: { "Output": "fs/dax.c=1497=int dax_file_unshare(struct inode inode, loff_t pos, loff_t len,\n--\nfs/dax.c-1499-{\nfs/dax.c:1500:\tstruct iomap_iter iter = {\nfs/dax.c-1501-\t\t.inode\t\t= inode,\n--\nfs/dax.c=1589=int dax_zero_range(struct inode inode, loff_t pos, loff_t len, bool did_zero,\n--\nfs/dax.c-1591-{\nfs/dax.c:1592:\tstruct iomap_iter iter = {\nfs/dax.c-1593-\t\t.inode\t\t= inode,\n--\nfs/dax.c=1902=static vm_fault_t dax_iomap_pte_fault(struct vm_fault vmf, unsigned long pfnp,\n--\nfs/dax.c-1906-\tXA_STATE(xas, \u0026mapping-\u003ei_pages, vmf-\u003epgoff);\nfs/dax.c:1907:\tstruct iomap_iter iter = {\nfs/dax.c-1908-\t\t.inode\t\t= mapping-\u003ehost,\n--\nfs/dax.c=2012=static vm_fault_t dax_iomap_pmd_fault(struct vm_fault vmf, unsigned long pfnp,\n--\nfs/dax.c-2016-\tXA_STATE_ORDER(xas, \u0026mapping-\u003ei_pages, vmf-\u003epgoff, PMD_ORDER);\nfs/dax.c:2017:\tstruct iomap_iter iter = {\nfs/dax.c-2018-\t\t.inode\t\t= mapping-\u003ehost,\n--\nfs/iomap/buffered-io.c=651=void iomap_read_folio(const struct iomap_ops ops,\n--\nfs/iomap/buffered-io.c-654-\tstruct folio folio = ctx-\u003ecur_folio;\nfs/iomap/buffered-io.c:655:\tstruct iomap_iter iter = {\nfs/iomap/buffered-io.c-656-\t\t.inode\t\t= folio-\u003emapping-\u003ehost,\n--\nfs/iomap/buffered-io.c=728=void iomap_readahead(const struct iomap_ops ops,\n--\nfs/iomap/buffered-io.c-731-\tstruct readahead_control rac = ctx-\u003erac;\nfs/iomap/buffered-io.c:732:\tstruct iomap_iter iter = {\nfs/iomap/buffered-io.c-733-\t\t.inode\t= rac-\u003emapping-\u003ehost,\n--\nfs/iomap/buffered-io.c=1294=iomap_file_buffered_write(struct kiocb iocb, struct iov_iter i,\n--\nfs/iomap/buffered-io.c-1297-{\nfs/iomap/buffered-io.c:1298:\tstruct iomap_iter iter = {\nfs/iomap/buffered-io.c-1299-\t\t.inode\t\t= iocb-\u003eki_filp-\u003ef_mapping-\u003ehost,\n--\nfs/iomap/buffered-io.c=1612=iomap_file_unshare(struct inode inode, loff_t pos, loff_t len,\n--\nfs/iomap/buffered-io.c-1615-{\nfs/iomap/buffered-io.c:1616:\tstruct iomap_iter iter = {\nfs/iomap/buffered-io.c-1617-\t\t.inode\t\t= inode,\n--\nfs/iomap/buffered-io.c=1740=iomap_zero_range(struct inode inode, loff_t pos, loff_t len, bool did_zero,\n--\nfs/iomap/buffered-io.c-1744-\tstruct folio_batch fbatch;\nfs/iomap/buffered-io.c:1745:\tstruct iomap_iter iter = {\nfs/iomap/buffered-io.c-1746-\t\t.inode\t\t= inode,\n--\nfs/iomap/buffered-io.c=1826=vm_fault_t iomap_page_mkwrite(struct vm_fault vmf, const struct iomap_ops ops,\n--\nfs/iomap/buffered-io.c-1828-{\nfs/iomap/buffered-io.c:1829:\tstruct iomap_iter iter = {\nfs/iomap/buffered-io.c-1830-\t\t.inode\t\t= file_inode(vmf-\u003evma-\u003evm_file),\n--\nfs/iomap/fiemap.c=58=int iomap_fiemap(struct inode inode, struct fiemap_extent_info fi,\n--\nfs/iomap/fiemap.c-60-{\nfs/iomap/fiemap.c:61:\tstruct iomap_iter iter = {\nfs/iomap/fiemap.c-62-\t\t.inode\t\t= inode,\n--\nfs/iomap/fiemap.c=94=iomap_bmap(struct address_space mapping, sector_t bno,\n--\nfs/iomap/fiemap.c-96-{\nfs/iomap/fiemap.c:97:\tstruct iomap_iter iter = {\nfs/iomap/fiemap.c-98-\t\t.inode\t= mapping-\u003ehost,\n--\nfs/iomap/seek.c=30=iomap_seek_hole(struct inode inode, loff_t pos, const struct iomap_ops ops)\n--\nfs/iomap/seek.c-32-\tloff_t size = i_size_read(inode);\nfs/iomap/seek.c:33:\tstruct iomap_iter iter = {\nfs/iomap/seek.c-34-\t\t.inode\t= inode,\n--\nfs/iomap/seek.c=76=iomap_seek_data(struct inode inode, loff_t pos, const struct iomap_ops ops)\n--\nfs/iomap/seek.c-78-\tloff_t size = i_size_read(inode);\nfs/iomap/seek.c:79:\tstruct iomap_iter iter = {\nfs/iomap/seek.c-80-\t\t.inode\t= inode,\n--\nfs/iomap/swapfile.c=140=int iomap_swapfile_activate(struct swap_info_struct sis,\n--\nfs/iomap/swapfile.c-144-\tstruct inode *inode = swap_file-\u003ef_mapping-\u003ehost;\nfs/iomap/swapfile.c:145:\tstruct iomap_iter iter = {\nfs/iomap/swapfile.c-146-\t\t.inode\t= inode,\n" }
39/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 32835 output: 30 thoughts: 238 Thoughts: My Current Understanding of IOMAP Write Streams Okay, so if I understand this correctly, in C, when I partially initialize a `struct` like using `= { .inode = ... }`, the compiler zero-initializes the rest of the fields. That's good to know, and it's relevant because it tells me the `struct iomap` embedded within `struct iomap_iter` will be zero-ed out when I do that. Also, the `iomap_iter_continue` function makes a point of zeroing this structure out at the beginning of each iteration using `memset`. I see that. Now, looking deeper, in `iomap_dio_bio_iter_one`, there's this assignment: `bio->bi_write_stream = iter->iomap.write_stream;`. Then, in `fs/xfs/xfs_iomap.c`, I see `iomap->write_stream = READ_ONCE(VFS_I(ip)->i_write_stream);`. Ah, so the write stream is being populated from the inode, read atomically. That makes sense. But what about the `writepage` path? What's going on there? In `fs/iomap/ioend.c`, it's `bio->bi_write_stream = wpc->iomap.write_stream;`. Wait a minute, where does `wpc` come from? I need to find the definition or where it is populated. I'm going to do a quick search for `struct iomap_writepage_ctx` through the kernel code to understand the context of `wpc` better. It seems like the state is carried there and that is where the write stream should be found.
40/3	2026/09/23 06:47	tool	grepper	0m Args: { "Expression": "iomap_writepage_ctx", "PathPrefix": "fs/" } Results: { "Output": "fs/exfat/inode.c=275=static int exfat_writepages(struct address_space mapping,\n--\nfs/exfat/inode.c-277-{\nfs/exfat/inode.c:278:\tstruct iomap_writepage_ctx wpc = {\nfs/exfat/inode.c-279-\t\t.inode\t\t= mapping-\u003ehost,\n--\nfs/exfat/iomap.c=201=const struct iomap_ops exfat_write_iomap_ops = {\n--\nfs/exfat/iomap.c-210- /\nfs/exfat/iomap.c:211:static ssize_t exfat_writeback_range(struct iomap_writepage_ctx wpc,\nfs/exfat/iomap.c-212-\t\tstruct folio folio, u64 offset, unsigned int len, u64 end_pos)\n--\nfs/fuse/file.c=2180=static bool fuse_folios_need_send(struct fuse_conn fc, loff_t pos,\n--\nfs/fuse/file.c-2211-\nfs/fuse/file.c:2212:static ssize_t fuse_iomap_writeback_range(struct iomap_writepage_ctx wpc,\nfs/fuse/file.c-2213-\t\t\t\t\t struct folio folio, u64 pos,\n--\nfs/fuse/file.c-2271-\nfs/fuse/file.c:2272:static int fuse_iomap_writeback_submit(struct iomap_writepage_ctx wpc,\nfs/fuse/file.c-2273-\t\t\t\t int error)\n--\nfs/fuse/file.c=2295=static int fuse_writepages(struct address_space mapping,\n--\nfs/fuse/file.c-2300-\tstruct fuse_fill_wb_data data = {};\nfs/fuse/file.c:2301:\tstruct iomap_writepage_ctx wpc = {\nfs/fuse/file.c-2302-\t\t.inode = inode,\n--\nfs/fuse/file.c=2319=static int fuse_launder_folio(struct folio folio)\n--\nfs/fuse/file.c-2322-\tstruct fuse_fill_wb_data data = {};\nfs/fuse/file.c:2323:\tstruct iomap_writepage_ctx wpc = {\nfs/fuse/file.c-2324-\t\t.inode = folio-\u003emapping-\u003ehost,\n--\nfs/gfs2/aops.c=157=static int gfs2_writepages(struct address_space mapping,\n--\nfs/gfs2/aops.c-161-\tlong initial_nr_to_write = wbc-\u003enr_to_write;\nfs/gfs2/aops.c:162:\tstruct iomap_writepage_ctx wpc = {\nfs/gfs2/aops.c-163-\t\t.inode\t\t= mapping-\u003ehost,\n--\nfs/gfs2/bmap.c=2435=int __gfs2_punch_hole(struct file file, loff_t offset, loff_t length)\n--\nfs/gfs2/bmap.c-2507-\nfs/gfs2/bmap.c:2508:static ssize_t gfs2_writeback_range(struct iomap_writepage_ctx wpc,\nfs/gfs2/bmap.c-2509-\t\tstruct folio folio, u64 offset, unsigned int len, u64 end_pos)\n--\nfs/iomap/buffered-io.c=1887=EXPORT_SYMBOL_GPL(iomap_finish_folio_write);\nfs/iomap/buffered-io.c-1888-\nfs/iomap/buffered-io.c:1889:static int iomap_writeback_range(struct iomap_writepage_ctx wpc,\nfs/iomap/buffered-io.c-1890-\t\tstruct folio folio, u64 pos, u32 rlen, u64 end_pos,\n--\nfs/iomap/buffered-io.c=1922=static bool iomap_writeback_handle_eof(struct folio folio,\nfs/iomap/buffered-io.c:1923:\t\tstruct iomap_writepage_ctx wpc, u64 end_pos)\nfs/iomap/buffered-io.c-1924-{\n--\nfs/iomap/buffered-io.c-1979-\nfs/iomap/buffered-io.c:1980:int iomap_writeback_folio(struct iomap_writepage_ctx wpc, struct folio folio)\nfs/iomap/buffered-io.c-1981-{\n--\nfs/iomap/buffered-io.c=2069=int\nfs/iomap/buffered-io.c:2070:iomap_writepages(struct iomap_writepage_ctx wpc)\nfs/iomap/buffered-io.c-2071-{\n--\nfs/iomap/ioend.c=118=static void ioend_writeback_end_bio(struct bio bio)\n--\nfs/iomap/ioend.c-135- /\nfs/iomap/ioend.c:136:int iomap_ioend_writeback_submit(struct iomap_writepage_ctx wpc, int error)\nfs/iomap/ioend.c-137-{\n--\nfs/iomap/ioend.c=157=EXPORT_SYMBOL_GPL(iomap_ioend_writeback_submit);\nfs/iomap/ioend.c-158-\nfs/iomap/ioend.c:159:static struct iomap_ioend iomap_alloc_ioend(struct iomap_writepage_ctx wpc,\nfs/iomap/ioend.c-160-\t\tloff_t pos, u16 ioend_flags)\n--\nfs/iomap/ioend.c-174-\nfs/iomap/ioend.c:175:static bool iomap_can_add_to_ioend(struct iomap_writepage_ctx wpc, loff_t pos,\nfs/iomap/ioend.c-176-\t\tunsigned int map_len, u16 ioend_flags)\n--\nfs/iomap/ioend.c-215- /\nfs/iomap/ioend.c:216:ssize_t iomap_add_to_ioend(struct iomap_writepage_ctx wpc, struct folio folio,\nfs/iomap/ioend.c-217-\t\tloff_t pos, loff_t end_pos, unsigned int dirty_len)\n--\nfs/ntfs/aops.c=252=static int ntfs_writepages(struct address_space mapping,\n--\nfs/ntfs/aops.c-256-\tstruct ntfs_inode ni = NTFS_I(inode);\nfs/ntfs/aops.c:257:\tstruct iomap_writepage_ctx wpc = {\nfs/ntfs/aops.c-258-\t\t.inode\t\t= mapping-\u003ehost,\n--\nfs/ntfs/iomap.c=794=const struct iomap_ops ntfs_dio_iomap_ops = {\n--\nfs/ntfs/iomap.c-797-\nfs/ntfs/iomap.c:798:static ssize_t ntfs_writeback_range(struct iomap_writepage_ctx wpc,\nfs/ntfs/iomap.c-799-\t\tstruct folio folio, u64 offset, unsigned int len, u64 end_pos)\n--\nfs/ntfs3/inode.c=1142=static void ntfs_iomap_put_folio(struct inode inode, loff_t pos,\n--\nfs/ntfs3/inode.c-1162- /\nfs/ntfs3/inode.c:1163:static ssize_t ntfs_writeback_range(struct iomap_writepage_ctx wpc,\nfs/ntfs3/inode.c-1164-\t\t\t\t struct folio folio, u64 offset,\n--\nfs/ntfs3/inode.c=1199=static int ntfs_writepages(struct address_space mapping,\n--\nfs/ntfs3/inode.c-1204-\tstruct ntfs_inode ni = ntfs_i(inode);\nfs/ntfs3/inode.c:1205:\tstruct iomap_writepage_ctx wpc = {\nfs/ntfs3/inode.c-1206-\t\t.inode = inode,\n--\nfs/xfs/xfs_aops.c=28=struct xfs_writepage_ctx {\nfs/xfs/xfs_aops.c:29:\tstruct iomap_writepage_ctx ctx;\nfs/xfs/xfs_aops.c-30-\tunsigned int\t\tdata_seq;\n--\nfs/xfs/xfs_aops.c=34=static inline struct xfs_writepage_ctx \nfs/xfs/xfs_aops.c:35:XFS_WPC(struct iomap_writepage_ctx ctx)\nfs/xfs/xfs_aops.c-36-{\n--\nfs/xfs/xfs_aops.c=121=xfs_imap_valid(\nfs/xfs/xfs_aops.c:122:\tstruct iomap_writepage_ctx\twpc,\nfs/xfs/xfs_aops.c-123-\tstruct xfs_inode\t\tip,\n--\nfs/xfs/xfs_aops.c=159=xfs_map_blocks(\nfs/xfs/xfs_aops.c:160:\tstruct iomap_writepage_ctx wpc,\nfs/xfs/xfs_aops.c-161-\tloff_t\t\t\toffset,\n--\nfs/xfs/xfs_aops.c=319=xfs_writeback_range(\nfs/xfs/xfs_aops.c:320:\tstruct iomap_writepage_ctx wpc,\nfs/xfs/xfs_aops.c-321-\tstruct folio\t\tfolio,\n--\nfs/xfs/xfs_aops.c=352=xfs_writeback_submit(\nfs/xfs/xfs_aops.c:353:\tstruct iomap_writepage_ctx\twpc,\nfs/xfs/xfs_aops.c-354-\tint\t\t\t\terror)\n--\nfs/xfs/xfs_aops.c=392=struct xfs_zoned_writepage_ctx {\nfs/xfs/xfs_aops.c:393:\tstruct iomap_writepage_ctx\tctx;\nfs/xfs/xfs_aops.c-394-\tstruct xfs_open_zone\t\topen_zone;\n--\nfs/xfs/xfs_aops.c=397=static inline struct xfs_zoned_writepage_ctx \nfs/xfs/xfs_aops.c:398:XFS_ZWPC(struct iomap_writepage_ctx ctx)\nfs/xfs/xfs_aops.c-399-{\n--\nfs/xfs/xfs_aops.c=404=xfs_zoned_map_blocks(\nfs/xfs/xfs_aops.c:405:\tstruct iomap_writepage_ctx wpc,\nfs/xfs/xfs_aops.c-406-\tloff_t\t\t\toffset,\n--\nfs/xfs/xfs_aops.c=464=xfs_zoned_writeback_range(\nfs/xfs/xfs_aops.c:465:\tstruct iomap_writepage_ctx wpc,\nfs/xfs/xfs_aops.c-466-\tstruct folio\t\tfolio,\n--\nfs/xfs/xfs_aops.c=482=xfs_zoned_writeback_submit(\nfs/xfs/xfs_aops.c:483:\tstruct iomap_writepage_ctx\twpc,\nfs/xfs/xfs_aops.c-484-\tint\t\t\t\terror)\n--\nfs/zonefs/file.c=124=static void zonefs_readahead(struct readahead_control rac)\n--\nfs/zonefs/file.c-132- /\nfs/zonefs/file.c:133:static ssize_t zonefs_writeback_range(struct iomap_writepage_ctx wpc,\nfs/zonefs/file.c-134-\t\tstruct folio folio, u64 offset, unsigned len, u64 end_pos)\n--\nfs/zonefs/file.c=163=static int zonefs_writepages(struct address_space *mapping,\n--\nfs/zonefs/file.c-165-{\nfs/zonefs/file.c:166:\tstruct iomap_writepage_ctx wpc = {\nfs/zonefs/file.c-167-\t\t.inode\t\t= mapping-\u003ehost,\n" }
41/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 36929 output: 34 thoughts: 83 Thoughts: Here's my take on the initialization of `wpc`, as I understand it: Digging into wpc Initialization Okay, so I see they're using designated initializers when setting up `wpc`. That's smart; keeps things clean and readable. The beauty of this approach in C, of course, is that any members of the `struct iomap_writepage_ctx wpc` that aren't explicitly initialized are automatically zeroed out. This implicit zero-initialization is something I often rely on in my own code to avoid subtle bugs related to uninitialized variables. Now, I need to verify this assumption about the zero-initialization of `wpc.iomap` in the context of the XFS filesystem code. Let's head over to `fs/xfs/xfs_aops.c` and confirm exactly how they're handling the `wpc` initialization. Time to dive into the details and make sure there aren't any unexpected gotchas.
42/3	2026/09/23 06:47	tool	grepper	0m Args: { "Expression": "wpc", "PathPrefix": "fs/xfs/xfs_aops.c" } Results: { "Output": "fs/xfs/xfs_aops.c=121=xfs_imap_valid(\nfs/xfs/xfs_aops.c:122:\tstruct iomap_writepage_ctx\twpc,\nfs/xfs/xfs_aops.c-123-\tstruct xfs_inode\t\tip,\n--\nfs/xfs/xfs_aops.c-125-{\nfs/xfs/xfs_aops.c:126:\tif (offset \u003c wpc-\u003eiomap.offset \|\|\nfs/xfs/xfs_aops.c:127:\t offset \u003e= wpc-\u003eiomap.offset + wpc-\u003eiomap.length)\nfs/xfs/xfs_aops.c-128-\t\treturn false;\n--\nfs/xfs/xfs_aops.c-133-\t /\nfs/xfs/xfs_aops.c:134:\tif (wpc-\u003eiomap.flags \u0026 IOMAP_F_SHARED)\nfs/xfs/xfs_aops.c-135-\t\treturn true;\n--\nfs/xfs/xfs_aops.c-143-\t /\nfs/xfs/xfs_aops.c:144:\tif (XFS_WPC(wpc)-\u003edata_seq != READ_ONCE(ip-\u003ei_df.if_seq)) {\nfs/xfs/xfs_aops.c:145:\t\ttrace_xfs_wb_data_iomap_invalid(ip, \u0026wpc-\u003eiomap,\nfs/xfs/xfs_aops.c:146:\t\t\t\tXFS_WPC(wpc)-\u003edata_seq, XFS_DATA_FORK);\nfs/xfs/xfs_aops.c-147-\t\treturn false;\n--\nfs/xfs/xfs_aops.c-149-\tif (xfs_inode_has_cow_data(ip) \u0026\u0026\nfs/xfs/xfs_aops.c:150:\t XFS_WPC(wpc)-\u003ecow_seq != READ_ONCE(ip-\u003ei_cowfp-\u003eif_seq)) {\nfs/xfs/xfs_aops.c:151:\t\ttrace_xfs_wb_cow_iomap_invalid(ip, \u0026wpc-\u003eiomap,\nfs/xfs/xfs_aops.c:152:\t\t\t\tXFS_WPC(wpc)-\u003ecow_seq, XFS_COW_FORK);\nfs/xfs/xfs_aops.c-153-\t\treturn false;\n--\nfs/xfs/xfs_aops.c=159=xfs_map_blocks(\nfs/xfs/xfs_aops.c:160:\tstruct iomap_writepage_ctx wpc,\nfs/xfs/xfs_aops.c-161-\tloff_t\t\t\toffset,\n--\nfs/xfs/xfs_aops.c-163-{\nfs/xfs/xfs_aops.c:164:\tstruct xfs_inode\tip = XFS_I(wpc-\u003einode);\nfs/xfs/xfs_aops.c-165-\tstruct xfs_mount\tmp = ip-\u003ei_mount;\nfs/xfs/xfs_aops.c:166:\tssize_t\t\t\tcount = i_blocksize(wpc-\u003einode);\nfs/xfs/xfs_aops.c-167-\txfs_fileoff_t\t\toffset_fsb = XFS_B_TO_FSBT(mp, offset);\n--\nfs/xfs/xfs_aops.c-196-\t /\nfs/xfs/xfs_aops.c:197:\tif (xfs_imap_valid(wpc, ip, offset))\nfs/xfs/xfs_aops.c-198-\t\treturn 0;\n--\nfs/xfs/xfs_aops.c-219-\tif (cow_fsb != NULLFILEOFF \u0026\u0026 cow_fsb \u003c= offset_fsb) {\nfs/xfs/xfs_aops.c:220:\t\tXFS_WPC(wpc)-\u003ecow_seq = READ_ONCE(ip-\u003ei_cowfp-\u003eif_seq);\nfs/xfs/xfs_aops.c-221-\t\txfs_iunlock(ip, XFS_ILOCK_SHARED);\n--\nfs/xfs/xfs_aops.c-230-\t /\nfs/xfs/xfs_aops.c:231:\tif (xfs_imap_valid(wpc, ip, offset)) {\nfs/xfs/xfs_aops.c-232-\t\txfs_iunlock(ip, XFS_ILOCK_SHARED);\n--\nfs/xfs/xfs_aops.c-242-\t\timap.br_startoff = end_fsb;\t/ fake a hole past EOF /\nfs/xfs/xfs_aops.c:243:\tXFS_WPC(wpc)-\u003edata_seq = READ_ONCE(ip-\u003ei_df.if_seq);\nfs/xfs/xfs_aops.c-244-\txfs_iunlock(ip, XFS_ILOCK_SHARED);\n--\nfs/xfs/xfs_aops.c-268-\nfs/xfs/xfs_aops.c:269:\txfs_bmbt_to_iomap(ip, \u0026wpc-\u003eiomap, \u0026imap, 0, 0, XFS_WPC(wpc)-\u003edata_seq);\nfs/xfs/xfs_aops.c-270-\ttrace_xfs_map_blocks_found(ip, offset, count, whichfork, \u0026imap);\n--\nfs/xfs/xfs_aops.c-279-\tif (whichfork == XFS_COW_FORK)\nfs/xfs/xfs_aops.c:280:\t\tseq = \u0026XFS_WPC(wpc)-\u003ecow_seq;\nfs/xfs/xfs_aops.c-281-\telse\nfs/xfs/xfs_aops.c:282:\t\tseq = \u0026XFS_WPC(wpc)-\u003edata_seq;\nfs/xfs/xfs_aops.c-283-\nfs/xfs/xfs_aops.c-284-\terror = xfs_bmapi_convert_delalloc(ip, whichfork, offset,\nfs/xfs/xfs_aops.c:285:\t\t\t\t\u0026wpc-\u003eiomap, seq);\nfs/xfs/xfs_aops.c-286-\tif (error) {\n--\nfs/xfs/xfs_aops.c-307-\nfs/xfs/xfs_aops.c:308:\t\tif (cow_offset \u003c wpc-\u003eiomap.offset + wpc-\u003eiomap.length)\nfs/xfs/xfs_aops.c:309:\t\t\twpc-\u003eiomap.length = cow_offset - wpc-\u003eiomap.offset;\nfs/xfs/xfs_aops.c-310-\t}\nfs/xfs/xfs_aops.c-311-\nfs/xfs/xfs_aops.c:312:\tASSERT(wpc-\u003eiomap.offset \u003c= offset);\nfs/xfs/xfs_aops.c:313:\tASSERT(wpc-\u003eiomap.offset + wpc-\u003eiomap.length \u003e offset);\nfs/xfs/xfs_aops.c-314-\ttrace_xfs_map_blocks_alloc(ip, offset, count, whichfork, \u0026imap);\n--\nfs/xfs/xfs_aops.c=319=xfs_writeback_range(\nfs/xfs/xfs_aops.c:320:\tstruct iomap_writepage_ctx wpc,\nfs/xfs/xfs_aops.c-321-\tstruct folio\t\tfolio,\n--\nfs/xfs/xfs_aops.c-327-\nfs/xfs/xfs_aops.c:328:\tret = xfs_map_blocks(wpc, offset, len);\nfs/xfs/xfs_aops.c-329-\tif (!ret)\nfs/xfs/xfs_aops.c:330:\t\tret = iomap_add_to_ioend(wpc, folio, offset, end_pos, len);\nfs/xfs/xfs_aops.c-331-\tif (ret \u003c 0)\n--\nfs/xfs/xfs_aops.c=352=xfs_writeback_submit(\nfs/xfs/xfs_aops.c:353:\tstruct iomap_writepage_ctx\twpc,\nfs/xfs/xfs_aops.c-354-\tint\t\t\t\terror)\nfs/xfs/xfs_aops.c-355-{\nfs/xfs/xfs_aops.c:356:\tstruct iomap_ioend\t\tioend = wpc-\u003ewb_ctx;\nfs/xfs/xfs_aops.c-357-\n--\nfs/xfs/xfs_aops.c-383-\nfs/xfs/xfs_aops.c:384:\treturn iomap_ioend_writeback_submit(wpc, error);\nfs/xfs/xfs_aops.c-385-}\n--\nfs/xfs/xfs_aops.c=404=xfs_zoned_map_blocks(\nfs/xfs/xfs_aops.c:405:\tstruct iomap_writepage_ctx wpc,\nfs/xfs/xfs_aops.c-406-\tloff_t\t\t\toffset,\n--\nfs/xfs/xfs_aops.c-408-{\nfs/xfs/xfs_aops.c:409:\tstruct xfs_inode\tip = XFS_I(wpc-\u003einode);\nfs/xfs/xfs_aops.c-410-\tstruct xfs_mount\tmp = ip-\u003ei_mount;\n--\nfs/xfs/xfs_aops.c-444-\t\txfs_iunlock(ip, XFS_ILOCK_EXCL);\nfs/xfs/xfs_aops.c:445:\t\txfs_bmbt_to_iomap(ip, \u0026wpc-\u003eiomap, \u0026imap, 0, 0, 0);\nfs/xfs/xfs_aops.c-446-\t\treturn 0;\n--\nfs/xfs/xfs_aops.c-456-\nfs/xfs/xfs_aops.c:457:\txfs_iomap_set_anon_write(ip, \u0026wpc-\u003eiomap, offset,\nfs/xfs/xfs_aops.c-458-\t\t\tXFS_FSB_TO_B(mp, count_fsb));\nfs/xfs/xfs_aops.c:459:\ttrace_xfs_zoned_map_blocks(ip, offset, wpc-\u003eiomap.length);\nfs/xfs/xfs_aops.c-460-\treturn 0;\n--\nfs/xfs/xfs_aops.c=464=xfs_zoned_writeback_range(\nfs/xfs/xfs_aops.c:465:\tstruct iomap_writepage_ctx wpc,\nfs/xfs/xfs_aops.c-466-\tstruct folio\t\tfolio,\n--\nfs/xfs/xfs_aops.c-472-\nfs/xfs/xfs_aops.c:473:\tret = xfs_zoned_map_blocks(wpc, offset, len);\nfs/xfs/xfs_aops.c-474-\tif (!ret)\nfs/xfs/xfs_aops.c:475:\t\tret = iomap_add_to_ioend(wpc, folio, offset, end_pos, len);\nfs/xfs/xfs_aops.c-476-\tif (ret \u003c 0)\n--\nfs/xfs/xfs_aops.c=482=xfs_zoned_writeback_submit(\nfs/xfs/xfs_aops.c:483:\tstruct iomap_writepage_ctx\twpc,\nfs/xfs/xfs_aops.c-484-\tint\t\t\t\terror)\nfs/xfs/xfs_aops.c-485-{\nfs/xfs/xfs_aops.c:486:\tstruct iomap_ioend\t\tioend = wpc-\u003ewb_ctx;\nfs/xfs/xfs_aops.c-487-\n--\nfs/xfs/xfs_aops.c-500-\t}\nfs/xfs/xfs_aops.c:501:\tif (wpc-\u003eiomap.flags \u0026 IOMAP_F_INTEGRITY)\nfs/xfs/xfs_aops.c-502-\t\tfs_bio_integrity_generate(\u0026ioend-\u003eio_bio);\nfs/xfs/xfs_aops.c:503:\txfs_zone_alloc_and_submit(ioend, \u0026XFS_ZWPC(wpc)-\u003eopen_zone);\nfs/xfs/xfs_aops.c-504-\treturn 0;\n--\nfs/xfs/xfs_aops.c=513=xfs_vm_writepages(\n--\nfs/xfs/xfs_aops.c-535-\t} else {\nfs/xfs/xfs_aops.c:536:\t\tstruct xfs_writepage_ctx\twpc = {\nfs/xfs/xfs_aops.c-537-\t\t\t.ctx = {\n--\nfs/xfs/xfs_aops.c-543-\nfs/xfs/xfs_aops.c:544:\t\treturn iomap_writepages(\u0026wpc.ctx);\nfs/xfs/xfs_aops.c-545-\t}\n" }
43/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 40893 output: 36 thoughts: 307 Thoughts: Investigating Potential IOMAP Write Stream Bug Okay, so I'm digging into a potential issue related to how the `write_stream` field in the `iomap` structure is handled, specifically within the context of writepage operations. I was looking at `xfs_vm_writepages` and I see that a `struct xfs_writepage_ctx wpc` is initialized, but I'm thinking about the implications. Then, looking at `xfs_bmbt_to_iomap`, there is the line `iomap->write_stream = READ_ONCE(VFS_I(ip)->i_write_stream);` My concern is what happens if another filesystem's iomap implementation doesn't explicitly set this `write_stream` field? It seems like there are multiple places it can be zeroed out. Initializations like `memset(&wpc->iomap, 0, ...)` or `struct iomap_writepage_ctx wpc = { .inode = ... }` could potentially zero it. Also, `iomap_iter_continue` could do it. I have to think about the initial state in the `iomap_begin` function in other filesystems. So the question is: what is the initial state of `iomap` in other filesystem's `iomap_begin` implementation? Does the `iomap_iter` structure zero out `iter->iomap` before calling the filesystem's `ops->iomap_begin` function? Let me look at the `iomap_iter_next` function in `fs/iomap/iter.c` to figure this out. I need to understand this iterator flow and the initialization. Let's start by reviewing lines 20-65 of that file. That should give me the core context.
44/3	2026/09/23 06:47	tool	read-file	0m Args: { "File": "fs/iomap/iter.c", "FirstLine": 20, "LineCount": 45 } Results: { "Contents": " 20:\t\t\tfolio_batch_release(iter-\u003efbatch);\n 21:\t\t\tfolio_batch_reinit(iter-\u003efbatch);\n 22:\t\t}\n 23:\t}\n 24:\t\n 25:\t/* Advance the current iterator position and decrement the remaining length /\n 26:\tint iomap_iter_advance(struct iomap_iter iter, u64 count)\n 27:\t{\n 28:\t\tif (WARN_ON_ONCE(count \u003e iomap_length(iter)))\n 29:\t\t\treturn -EIO;\n 30:\t\titer-\u003epos += count;\n 31:\t\titer-\u003elen -= count;\n 32:\t\treturn 0;\n 33:\t}\n 34:\t\n 35:\tstatic inline void iomap_iter_done(struct iomap_iter iter)\n 36:\t{\n 37:\t\tWARN_ON_ONCE(iter-\u003eiomap.offset \u003e iter-\u003epos);\n 38:\t\tWARN_ON_ONCE(iter-\u003eiomap.length == 0);\n 39:\t\tWARN_ON_ONCE(iter-\u003eiomap.offset + iter-\u003eiomap.length \u003c= iter-\u003epos);\n 40:\t\tWARN_ON_ONCE(iter-\u003eiomap.flags \u0026 IOMAP_F_STALE);\n 41:\t\n 42:\t\titer-\u003eiter_start_pos = iter-\u003epos;\n 43:\t\n 44:\t\ttrace_iomap_iter_dstmap(iter-\u003einode, \u0026iter-\u003eiomap);\n 45:\t\tif (iter-\u003esrcmap.type != IOMAP_HOLE)\n 46:\t\t\ttrace_iomap_iter_srcmap(iter-\u003einode, \u0026iter-\u003esrcmap);\n 47:\t}\n 48:\t\n 49:\t/\n 50:\t iomap_iter_continue - decide whether iteration should continue\n 51:\t * @iter: iteration structure\n 52:\t * @iomap: the mapping that was just processed\n 53:\t * @srcmap: the source mapping that was just processed\n 54:\t \n 55:\t Helper normally called via iomap_iter_next(). Called after the previous\n 56:\t * mapping has been finished to determine whether there is more of the file\n 57:\t * range left to process.\n 58:\t \n 59:\t Returns 1 if there is more work to do, in which case @iomap and @srcmap are\n 60:\t * cleared so the caller can produce the next mapping; zero if the range is\n 61:\t * fully consumed; or a negative errno on error.\n 62:\t /\n 63:\tint iomap_iter_continue(const struct iomap_iter iter, struct iomap iomap,\n 64:\t\t\tstruct iomap srcmap, int ret)\n" }
45/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 42383 output: 32 thoughts: 21 Thoughts: Here's my thought process, as if I were thinking it: Digging into `iomap_iter_next` Okay, so I need to understand where `iomap_iter_next` is defined. It's a key function, and knowing its origin is essential for debugging or understanding the broader architecture. I could manually sift through headers, but that's going to be inefficient. Time to leverage the tools at my disposal. Grepping is the quickest way to track this function down. Let's see what grepper unearths.
46/3	2026/09/23 06:47	tool	grepper	0m Args: { "Expression": "iomap_iter_next", "PathPrefix": "fs/iomap" } Results: { "Output": "fs/iomap/iter.c=35=static inline void iomap_iter_done(struct iomap_iter iter)\n--\nfs/iomap/iter.c-54- \nfs/iomap/iter.c:55: * Helper normally called via iomap_iter_next(). Called after the previous\nfs/iomap/iter.c-56- * mapping has been finished to determine whether there is more of the file\n--\nfs/iomap/iter.c=115=int iomap_iter(struct iomap_iter iter, const struct iomap_ops ops)\n--\nfs/iomap/iter.c-123-\telse\nfs/iomap/iter.c:124:\t\tret = iomap_iter_next(iter, \u0026iter-\u003eiomap, \u0026iter-\u003esrcmap,\nfs/iomap/iter.c-125-\t\t\t\tops-\u003eiomap_begin, ops-\u003eiomap_end);\n" }
47/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 42813 output: 37 thoughts: 26 Thoughts: Okay, let's dive into this. Here's my take on those lines of code: Analyzing `fs/iomap/iter.c` (Lines 130-200) Alright, so I'm looking at `fs/iomap/iter.c`, specifically lines 130 to 200, to get a handle on what's going on within that section. Given the context, I'm expecting this to be the core logic involved in iterating through an iomap. It's probably the part that translates a logical view of the file data into a series of physical extents or blocks for actual I/O. I'm focusing on this region because it likely handles the complexities of iomap structures, including dealing with holes, different mapping types, and perhaps even some optimization for read/write patterns. I want to see if they're doing something clever to minimize metadata lookups. I'm also interested in how they're handling errors and partial reads/writes within this iteration process. Are there any implicit assumptions about block size, and how is it all orchestrated with the underlying block device interface? I'm trying to determine whether they are using a typical iterator pattern, a state machine, or something more advanced to track and manage the current position within the iomap. Are they doing any look-ahead processing? Are there any obvious potential performance bottlenecks here? I want to see how elegant and efficient this iteration logic is, especially in a concurrent environment. My experience with file systems tells me there is likely an attempt to optimize by merging adjacent extents and perhaps using a prefetch strategy.
48/3	2026/09/23 06:47	tool	read-file	0m Args: { "File": "fs/iomap/iter.c", "FirstLine": 130, "LineCount": 60 } Results: { "Contents": " 130:\t\telse if (ret \u003c 0)\n 131:\t\t\tiomap_iter_clean_fbatch(iter, \u0026iter-\u003eiomap);\n 132:\t\n 133:\t\treturn ret;\n 134:\t}\n" }
49/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 43301 output: 21 thoughts: 44 Thoughts: Okay, let's see. Navigating the I/O Mapping Iteration Right, so I was just looking at the end of `fs/iomap/iter.c` – line 134, specifically – and that marked the... end of the file? Hmm. I was expecting to find the `iomap_iter_next` function there, but it appears to not be. Okay, no problem, let's not waste any time. Time to fire up the trusty `grepper` and see where that function is actually defined. Let's see if we can locate it quickly...
50/3	2026/09/23 06:47	tool	grepper	0m Args: { "Expression": "iomap_iter_next" } Results: { "Output": "fs/iomap/iter.c=35=static inline void iomap_iter_done(struct iomap_iter iter)\n--\nfs/iomap/iter.c-54- \nfs/iomap/iter.c:55: * Helper normally called via iomap_iter_next(). Called after the previous\nfs/iomap/iter.c-56- * mapping has been finished to determine whether there is more of the file\n--\nfs/iomap/iter.c=115=int iomap_iter(struct iomap_iter iter, const struct iomap_ops ops)\n--\nfs/iomap/iter.c-123-\telse\nfs/iomap/iter.c:124:\t\tret = iomap_iter_next(iter, \u0026iter-\u003eiomap, \u0026iter-\u003esrcmap,\nfs/iomap/iter.c-125-\t\t\t\tops-\u003eiomap_begin, ops-\u003eiomap_end);\n--\ninclude/linux/iomap.h=232=typedef int (iomap_iter_end_fn)(struct inode inode, loff_t pos, loff_t length,\n--\ninclude/linux/iomap.h-239- /\ninclude/linux/iomap.h:240:typedef int (iomap_iter_next_fn)(const struct iomap_iter iter,\ninclude/linux/iomap.h-241-\t\tstruct iomap iomap, struct iomap srcmap);\n--\ninclude/linux/iomap.h=243=struct iomap_ops {\n--\ninclude/linux/iomap.h-245-\tiomap_iter_end_fn iomap_end;\ninclude/linux/iomap.h:246:\tiomap_iter_next_fn iomap_next;\ninclude/linux/iomap.h-247-};\n--\ninclude/linux/iomap.h=334=int iomap_iter_continue(const struct iomap_iter iter, struct iomap iomap,\n--\ninclude/linux/iomap.h-337-/\ninclude/linux/iomap.h:338: iomap_iter_next - finish the previous mapping and produce the next one\ninclude/linux/iomap.h-339- * @iter: iteration structure\n--\ninclude/linux/iomap.h-356- /\ninclude/linux/iomap.h:357:static __always_inline int iomap_iter_next(const struct iomap_iter iter,\ninclude/linux/iomap.h-358-\t\tstruct iomap iomap, struct iomap srcmap,\n--\ninclude/linux/iomap.h=390=int name(const struct iomap_iter iter, struct iomap iomap,\t\t\\\n--\ninclude/linux/iomap.h-392-{\t\t\t\t\t\t\t\t\t\\\ninclude/linux/iomap.h:393:\treturn iomap_iter_next(iter, iomap, srcmap, begin_fn, end_fn);\t\\\ninclude/linux/iomap.h-394-}\n" }
51/3	2026/09/23 06:47	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 44323 output: 37 thoughts: 23 Thoughts: Here's a summary of my mental process: Diving into the Kernel's I/O Mapping Okay, so I need to understand this specific area of the kernel's I/O mapping implementation better. My immediate instinct is to jump directly into the code. Let's start with the header file, specifically `include/linux/iomap.h`. I'll want to check around line 357. That's usually a good indicator of where a significant data structure or function definition might reside within the relevant section of code, and that's likely going to provide a good starting point for my investigation. I'm focusing on that area to get a handle on the current state of things.
52/3	2026/09/23 06:48	tool	read-file	0m Args: { "File": "include/linux/iomap.h", "FirstLine": 355, "LineCount": 40 } Results: { "Contents": " 355:\t * negative errno on error.\n 356:\t /\n 357:\tstatic __always_inline int iomap_iter_next(const struct iomap_iter iter,\n 358:\t\t\tstruct iomap iomap, struct iomap srcmap,\n 359:\t\t\tiomap_iter_begin_fn begin, iomap_iter_end_fn end)\n 360:\t{\n 361:\t\tint ret = 0;\n 362:\t\n 363:\t\tif (iomap-\u003elength) {\n 364:\t\t\tif (end) {\n 365:\t\t\t\t/\n 366:\t\t\t\t Calculate how far the iter was advanced and the\n 367:\t\t\t\t * original length bytes for end().\n 368:\t\t\t\t /\n 369:\t\t\t\tssize_t advanced = iter-\u003epos - iter-\u003eiter_start_pos;\n 370:\t\t\t\tloff_t len;\n 371:\t\n 372:\t\t\t\tlen = iomap_length_trim(iter, iter-\u003eiter_start_pos,\n 373:\t\t\t\t\t\titer-\u003elen + advanced);\n 374:\t\n 375:\t\t\t\tret = end(iter-\u003einode, iter-\u003eiter_start_pos, len,\n 376:\t\t\t\t\t\tadvanced, iter-\u003eflags, iomap);\n 377:\t\t\t}\n 378:\t\t\tret = iomap_iter_continue(iter, iomap, srcmap, ret);\n 379:\t\t\tif (ret \u003c= 0)\n 380:\t\t\t\treturn ret;\n 381:\t\t}\n 382:\t\n 383:\t\tret = begin(iter-\u003einode, iter-\u003epos, iter-\u003elen, iter-\u003eflags, iomap,\n 384:\t\t\t\tsrcmap);\n 385:\t\n 386:\t\treturn ret \u003c 0 ? ret : 1;\n 387:\t}\n 388:\t\n 389:\t#define DEFINE_IOMAP_ITER_NEXT_END(name, begin_fn, end_fn)\t\t\\\n 390:\tint name(const struct iomap_iter iter, struct iomap iomap,\t\t\\\n 391:\t\t\tstruct iomap srcmap)\t\t\t\t\t\\\n 392:\t{\t\t\t\t\t\t\t\t\t\\\n 393:\t\treturn iomap_iter_next(iter, iomap, srcmap, begin_fn, end_fn);\t\\\n 394:\t}\n" }
53/3	2026/09/23 06:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 45180 output: 32 thoughts: 102 Thoughts: Initial Thoughts on `iomap_iter_next` and Potential Zero-Initialization Issues Okay, so I'm looking at `iomap_iter_next`. On the first run, I'm thinking, `iomap->length` will be zero. That makes sense, because I remember how `iter` was declared—it was zero-initialized, usually with a designated initializer like `struct iomap_iter iter = { .inode = ... }`. But a nagging thought creeps in... what happens if someone doesn't zero-initialize it? What if the `iomap_iter` is declared without that explicit `= { ... }` or isn't explicitly zeroed out? That could lead to some nasty bugs if `length` isn't initialized to zero. I need to be sure this function behaves correctly in all scenarios. Time to dig through the kernel codebase and track down all instances of `struct iomap_iter` to see how it's being used and initialized. I need to understand the implications of non-zero initialization if that's even possible.
54/3	2026/09/23 06:48	tool	grepper	0m Error: no matches Args: { "Expression": "struct iomap_iter [a-zA-Z0-9_]+;" } Results: { "error": "no matches" }
55/3	2026/09/23 06:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 45561 output: 37 thoughts: 380 Thoughts: Analyzing the `iomap` Structure Okay, so I'm double-checking the code. I know there aren't any uninitialized `struct iomap_iter` variables floating around, so my focus is now on the `struct iomap` itself. Let me just glance at `include/linux/iomap.h` and see what's up with that structure. I remember there was a change recently... Yep, here it is: ```c struct iomap { u64 offset; /* offset of mapping, bytes / u64 flags; / flags for mapping / ... ``` Ah, right. I was expecting to see `write_stream` and was drawing a blank. Where was that added? Let's quickly diff the header file and refresh my memory. Line 130 seems to be the right spot, give or take. ```c diff --git a/include/linux/iomap.h b/include/linux/iomap.h index bc7ae6327dbf8..f923778f08bd7 100644 --- a/include/linux/iomap.h +++ b/include/linux/iomap.h @@ -133,6 +133,7 @@ struct iomap { u64 length; / length of mapping, bytes / u16 type; / type of mapping / u16 flags; / flags for mapping / + u16 write_stream; / write stream for I/O / struct block_device bdev; /* block device for I/O / struct dax_device dax_dev; /* dax_dev for dax operations / void inline_data; ``` Ah, there it is! `write_stream` was added as a `u16` right where I suspected. Now, let's just make sure I have the context right and read the section between lines 125-150 for a full review. Got it.
56/3	2026/09/23 06:48	tool	read-file	0m Args: { "File": "include/linux/iomap.h", "FirstLine": 125, "LineCount": 25 } Results: { "Contents": " 125:\t/\n 126:\t Magic value for addr:\n 127:\t /\n 128:\t#define IOMAP_NULL_ADDR -1ULL\t/ addr is not valid /\n 129:\t\n 130:\tstruct iomap {\n 131:\t\tu64\t\t\taddr; / disk offset of mapping, bytes /\n 132:\t\tloff_t\t\t\toffset;\t/ file offset of mapping, bytes /\n 133:\t\tu64\t\t\tlength;\t/ length of mapping, bytes /\n 134:\t\tu16\t\t\ttype;\t/ type of mapping /\n 135:\t\tu16\t\t\tflags;\t/ flags for mapping /\n 136:\t\tu16\t\t\twrite_stream; / write stream for I/O /\n 137:\t\tstruct block_device\tbdev;\t/* block device for I/O /\n 138:\t\tstruct dax_device\tdax_dev; /* dax_dev for dax operations /\n 139:\t\tvoid\t\t\tinline_data;\n 140:\t\tvoid\t\t\tprivate; / filesystem private /\n 141:\t\tu64\t\t\tvalidity_cookie; / used with .iomap_valid() /\n 142:\t};\n 143:\t\n 144:\tstatic inline sector_t iomap_sector(const struct iomap iomap, loff_t pos)\n 145:\t{\n 146:\t\tif (iomap-\u003eflags \u0026 IOMAP_F_ANON_WRITE)\n 147:\t\t\treturn U64_MAX; /* invalid */\n 148:\t\treturn (iomap-\u003eaddr + pos - iomap-\u003eoffset) \u003e\u003e SECTOR_SHIFT;\n 149:\t}\n" }
57/3	2026/09/23 06:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 46929 output: 30 thoughts: 210 Thoughts: Analyzing the Impact of the iomap Structure Modification Okay, so I'm looking at this change and immediately I'm noticing a potential alignment concern within the `iomap` structure. We have `type` and `flags` as `u16` types, which is interesting, and before this patch there was a sizable 32-bit hole -- 4 bytes of padding -- before the `block_device bdev` pointer on 64-bit architectures, due to the pointer alignment requirements, following the initial 16 + 16 bit values. Now, the introduction of `u16 write_stream` seems to have eaten up half of that padding, leaving a mere 16 bits remaining. My immediate thought is, "Wait, is this safe? Could a user process somehow copy this `iomap` structure into user space?" If that happened, this padding manipulation could become a source of subtle, hard-to-debug problems. We'd have to make sure that whatever's copying this around does so correctly. But, hang on... let's think this through. Is `struct iomap` ever actually* copied to user space? I believe it's not. My understanding is that `struct iomap` is strictly an internal kernel structure, used only within the kernel's memory space. For user-facing interactions like `fiemap`, we're using `struct fiemap_extent`, which is defined and utilized, and that's all translated within `fs/iomap/fiemap.c`. To be absolutely certain, let's just go double check `fs/iomap/fiemap.c`. We need to eliminate any doubt!
58/3	2026/09/23 06:48	tool	grepper	0m Error: no matches Args: { "Expression": "copy_to_user", "PathPrefix": "fs/iomap" } Results: { "error": "no matches" }
59/3	2026/09/23 06:48	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 47554 output: 58 thoughts: 1922 Thoughts: Write Stream ioctl Analysis and Initialization Checks Okay, so I'm looking at these new write stream ioctls in `fs/iomap` and specifically, I'm trying to determine if there are any potential memory exposure issues related to uninitialized data being copied to or from user space. I've already confirmed there's no `copy_to_user` in `fs/iomap`, but I need to make sure I'm not missing anything. First, I checked the new ioctl definitions in `include/uapi/linux/fs.h`. I see the new `FS_IOC_WRITE_STREAM_GET_MAX`, `FS_IOC_WRITE_STREAM_ALLOC`, and `FS_IOC_WRITE_STREAM_SET`. Then, I went through each of the ioctl implementations in `fs/xfs` to analyze them: 1. `FS_IOC_WRITE_STREAM_GET_MAX`: This uses `put_user` to return a `__u32`. The returned value, `max`, comes from `xfs_inode_max_write_streams(ip)`. It looks like `max` is fully assigned. There isn't any uninitialized memory being exposed here. 2. `FS_IOC_WRITE_STREAM_ALLOC`: This ioctl directly returns the file descriptor as the return value of the ioctl call (`int`). No `copy_to_user` or `put_user` calls here, so no risk. 3. `FS_IOC_WRITE_STREAM_SET`: This uses `copy_from_user` to read a `struct fs_write_stream_set` from user space. It doesn't copy anything back to user space, so no uninitialized data risk. Next, I looked at `struct inode` in `include/linux/fs.h`. I see `u16 i_write_stream`. I checked its initialization in `inode_init_always_gfp` and it's explicitly initialized to zero. That covers that. I also checked `fs/write_streams.c`, to see what kind of initialization happens for `struct write_stream`. The `write_stream` struct itself is allocated using `kzalloc_obj`, which guarantees zero-initialization. I checked how the `write_stream_pool` is initialized and destroyed. The `bitmap_zalloc` function also guarantees zeroed memory. I need to confirm initialization for `xfs_buftarg`, where is it allocated and initialized? I'll search for its allocation in `fs/xfs/xfs_buf.c` now to determine where `xfs_buftarg` is allocated and initialized to ensure it's not exposing uninitialized data.
60/3	2026/09/23 06:49	tool	grepper	0m Error: no matches Args: { "Expression": "kmem_zalloc.xfs_buftarg\|kmem_alloc.xfs_buftarg\|kzalloc.xfs_buftarg", "PathPrefix": "fs/xfs" } Results:* { "error": "no matches" }
61/3	2026/09/23 06:49	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 50151 output: 29 thoughts: 33 Thoughts: Here's my thought process, as if I were considering this myself: Tracing Down xfs_alloc_buftarg Okay, I need to understand how `xfs_alloc_buftarg`, or a similar function, is being used. Since this is an XFS-related function, my initial instinct is to look within the XFS filesystem code specifically. The name suggests this deals with buffers, so the most likely starting point is the `fs/xfs/` directory, and then the `xfs_buf.c` file feels like the logical place to begin digging. I'll search that file for the definition. That should give me the context I need to figure out the function's purpose within XFS's buffering strategy.
62/3	2026/09/23 06:49	tool	grepper	0m Args: { "Expression": "_buftarg\\(", "PathPrefix": "fs/xfs" } Results: { "Output": "fs/xfs/libxfs/xfs_btree.c=538=static inline struct xfs_buftarg \nfs/xfs/libxfs/xfs_btree.c:539:xfs_btree_buftarg(\nfs/xfs/libxfs/xfs_btree.c-540-\tstruct xfs_btree_cur\tcur)\n--\nfs/xfs/libxfs/xfs_btree.c=562=xfs_btree_dup_cursor(\n--\nfs/xfs/libxfs/xfs_btree.c-600-\t\t\terror = xfs_trans_read_buf(mp, tp,\nfs/xfs/libxfs/xfs_btree.c:601:\t\t\t\t\txfs_btree_buftarg(cur),\nfs/xfs/libxfs/xfs_btree.c-602-\t\t\t\t\txfs_buf_daddr(bp),\n--\nfs/xfs/libxfs/xfs_btree.c=1108=xfs_btree_readahead_ptr(\n--\nfs/xfs/libxfs/xfs_btree.c-1116-\t\treturn;\nfs/xfs/libxfs/xfs_btree.c:1117:\txfs_buf_readahead(xfs_btree_buftarg(cur), daddr,\nfs/xfs/libxfs/xfs_btree.c-1118-\t\t\txfs_btree_bbsize(cur) * count,\n--\nfs/xfs/libxfs/xfs_btree.c=1358=xfs_btree_get_buf_block(\n--\nfs/xfs/libxfs/xfs_btree.c-1369-\t\treturn error;\nfs/xfs/libxfs/xfs_btree.c:1370:\terror = xfs_trans_get_buf(cur-\u003ebc_tp, xfs_btree_buftarg(cur), d,\nfs/xfs/libxfs/xfs_btree.c-1371-\t\t\txfs_btree_bbsize(cur), 0, bpp);\n--\nfs/xfs/libxfs/xfs_btree.c=1385=xfs_btree_read_buf_block(\n--\nfs/xfs/libxfs/xfs_btree.c-1401-\t\treturn error;\nfs/xfs/libxfs/xfs_btree.c:1402:\terror = xfs_trans_read_buf(mp, cur-\u003ebc_tp, xfs_btree_buftarg(cur), d,\nfs/xfs/libxfs/xfs_btree.c-1403-\t\t\txfs_btree_bbsize(cur), flags, bpp,\n--\nfs/xfs/xfs_aops.c=549=xfs_dax_writepages(\n--\nfs/xfs/xfs_aops.c-556-\treturn dax_writeback_mapping_range(mapping,\nfs/xfs/xfs_aops.c:557:\t\t\txfs_inode_buftarg(ip)-\u003ebt_daxdev, wbc);\nfs/xfs/xfs_aops.c-558-}\n--\nfs/xfs/xfs_aops.c=602=xfs_get_iomap_read_ops(\n--\nfs/xfs/xfs_aops.c-606-\nfs/xfs/xfs_aops.c:607:\tif (bdev_has_integrity_csum(xfs_inode_buftarg(ip)-\u003ebt_bdev))\nfs/xfs/xfs_aops.c-608-\t\treturn \u0026xfs_iomap_read_ops;\n--\nfs/xfs/xfs_aops.c=635=xfs_vm_swap_activate(\n--\nfs/xfs/xfs_aops.c-673-\t /\nfs/xfs/xfs_aops.c:674:\tsis-\u003ebdev = xfs_inode_buftarg(ip)-\u003ebt_bdev;\nfs/xfs/xfs_aops.c-675-\n--\nfs/xfs/xfs_bmap_util.c=54=xfs_zero_extent(\n--\nfs/xfs/xfs_bmap_util.c-58-{\nfs/xfs/xfs_bmap_util.c:59:\treturn blkdev_issue_zeroout(xfs_inode_buftarg(ip)-\u003ebt_bdev,\nfs/xfs/xfs_bmap_util.c-60-\t\t\txfs_fsb_to_db(ip, start_fsb),\n--\nfs/xfs/xfs_buf.c=1468=xfs_buftarg_drain_rele(\n--\nfs/xfs/xfs_buf.c-1481-\t\tspin_unlock(\u0026bp-\u003eb_lockref.lock);\nfs/xfs/xfs_buf.c:1482:\t\ttrace_xfs_buf_drain_buftarg(bp, _RET_IP_);\nfs/xfs/xfs_buf.c-1483-\t\treturn LRU_SKIP;\n--\nfs/xfs/xfs_buf.c=1635=void\nfs/xfs/xfs_buf.c:1636:xfs_destroy_buftarg(\nfs/xfs/xfs_buf.c-1637-\tstruct xfs_buftarg\tbtp)\n--\nfs/xfs/xfs_buf.c=1646=void\nfs/xfs/xfs_buf.c:1647:xfs_free_buftarg(\nfs/xfs/xfs_buf.c-1648-\tstruct xfs_buftarg\tbtp)\n--\nfs/xfs/xfs_buf.c-1650-\twrite_stream_pool_destroy(\u0026btp-\u003ebt_stream_pool);\nfs/xfs/xfs_buf.c:1651:\txfs_destroy_buftarg(btp);\nfs/xfs/xfs_buf.c-1652-\tfs_put_dax(btp-\u003ebt_daxdev, btp-\u003ebt_mount);\n--\nfs/xfs/xfs_buf.c=1723=int\nfs/xfs/xfs_buf.c:1724:xfs_configure_buftarg(\nfs/xfs/xfs_buf.c-1725-\tstruct xfs_buftarg\tbtp,\n--\nfs/xfs/xfs_buf.c=1753=int\nfs/xfs/xfs_buf.c:1754:xfs_init_buftarg(\nfs/xfs/xfs_buf.c-1755-\tstruct xfs_buftarg\t\tbtp,\n--\nfs/xfs/xfs_buf.c=1799=struct xfs_buftarg \nfs/xfs/xfs_buf.c:1800:xfs_alloc_buftarg(\nfs/xfs/xfs_buf.c-1801-\tstruct xfs_mount\tmp,\n--\nfs/xfs/xfs_buf.c-1835-\nfs/xfs/xfs_buf.c:1836:\terror = xfs_init_buftarg(btp, btp-\u003ebt_meta_sectorsize,\nfs/xfs/xfs_buf.c-1837-\t\t\t\tmp-\u003em_super-\u003es_id);\n--\nfs/xfs/xfs_buf.h=351=xfs_buf_update_cksum(struct xfs_buf bp, unsigned long cksum_offset)\n--\nfs/xfs/xfs_buf.h-359- /\nfs/xfs/xfs_buf.h:360:struct xfs_buftarg xfs_alloc_buftarg(struct xfs_mount mp,\nfs/xfs/xfs_buf.h-361-\t\tstruct file bdev_file);\nfs/xfs/xfs_buf.h:362:extern void xfs_free_buftarg(struct xfs_buftarg );\nfs/xfs/xfs_buf.h-363-extern void xfs_buftarg_wait(struct xfs_buftarg );\nfs/xfs/xfs_buf.h=364=extern void xfs_buftarg_drain(struct xfs_buftarg );\nfs/xfs/xfs_buf.h:365:int xfs_configure_buftarg(struct xfs_buftarg btp, unsigned int sectorsize,\nfs/xfs/xfs_buf.h-366-\t\txfs_fsblock_t nr_blocks);\nfs/xfs/xfs_buf.h=367=int xfs_buftarg_init_streams(struct xfs_buftarg btp,\n--\nfs/xfs/xfs_buf.h-369-\nfs/xfs/xfs_buf.h:370:#define xfs_readonly_buftarg(buftarg)\tbdev_read_only((buftarg)-\u003ebt_bdev)\nfs/xfs/xfs_buf.h-371-\n--\nfs/xfs/xfs_buf.h=373=bool xfs_verify_magic16(struct xfs_buf bp, __be16 dmagic);\n--\nfs/xfs/xfs_buf.h-375-/* for xfs_buf_mem.c only: /\nfs/xfs/xfs_buf.h:376:int xfs_init_buftarg(struct xfs_buftarg btp, size_t logical_sectorsize,\nfs/xfs/xfs_buf.h-377-\t\tconst char descr);\nfs/xfs/xfs_buf.h:378:void xfs_destroy_buftarg(struct xfs_buftarg btp);\nfs/xfs/xfs_buf.h-379-\n--\nfs/xfs/xfs_buf_mem.c=51=xmbuf_alloc(\n--\nfs/xfs/xfs_buf_mem.c-91-\nfs/xfs/xfs_buf_mem.c:92:\terror = xfs_init_buftarg(btp, XMBUF_BLOCKSIZE, descr);\nfs/xfs/xfs_buf_mem.c-93-\tif (error)\n--\nfs/xfs/xfs_buf_mem.c=110=xmbuf_free(\n--\nfs/xfs/xfs_buf_mem.c-117-\nfs/xfs/xfs_buf_mem.c:118:\txfs_destroy_buftarg(btp);\nfs/xfs/xfs_buf_mem.c-119-\tfput(btp-\u003ebt_file);\n--\nfs/xfs/xfs_discard.c=112=xfs_discard_extents(\n--\nfs/xfs/xfs_discard.c-123-\t\tstruct xfs_buftarg\tbtp =\nfs/xfs/xfs_discard.c:124:\t\t\txfs_group_type_buftarg(xg-\u003exg_mount, xg-\u003exg_type);\nfs/xfs/xfs_discard.c-125-\n--\nfs/xfs/xfs_file.c=125=xfs_file_fsync(\n--\nfs/xfs/xfs_file.c-167-\tif (!log_flushed)\nfs/xfs/xfs_file.c:168:\t\treturn blkdev_issue_flush(xfs_inode_buftarg(ip)-\u003ebt_bdev);\nfs/xfs/xfs_file.c-169-\treturn 0;\n--\nfs/xfs/xfs_file.c=808=xfs_file_dio_write_atomic(\n--\nfs/xfs/xfs_file.c-821-\t /\nfs/xfs/xfs_file.c:822:\tif (ocount \u003e xfs_inode_buftarg(ip)-\u003ebt_awu_max)\nfs/xfs/xfs_file.c-823-\t\tdops = \u0026xfs_atomic_write_cow_iomap_ops;\n--\nfs/xfs/xfs_file.c=960=xfs_file_dio_write(\n--\nfs/xfs/xfs_file.c-964-\tstruct xfs_inode\tip = XFS_I(file_inode(iocb-\u003eki_filp));\nfs/xfs/xfs_file.c:965:\tstruct xfs_buftarg target = xfs_inode_buftarg(ip);\nfs/xfs/xfs_file.c-966-\tsize_t\t\t\tcount = iov_iter_count(from);\n--\nfs/xfs/xfs_file.c=1361=xfs_falloc_write_zeroes(\n--\nfs/xfs/xfs_file.c-1378-\tif (xfs_is_always_cow_inode(ip) \|\| xfs_inode_has_bigrtalloc(ip) \|\|\nfs/xfs/xfs_file.c:1379:\t !bdev_write_zeroes_unmap_sectors(xfs_inode_buftarg(ip)-\u003ebt_bdev))\nfs/xfs/xfs_file.c-1380-\t\treturn -EOPNOTSUPP;\n--\nfs/xfs/xfs_file.c=2135=xfs_file_mmap_prepare(\n--\nfs/xfs/xfs_file.c-2139-\tstruct inode\t\tinode = file_inode(file);\nfs/xfs/xfs_file.c:2140:\tstruct xfs_buftarg\ttarget = xfs_inode_buftarg(XFS_I(inode));\nfs/xfs/xfs_file.c-2141-\n--\nfs/xfs/xfs_inode.c=53=xfs_inode_max_write_streams(\n--\nfs/xfs/xfs_inode.c-61-\t\treturn 0;\nfs/xfs/xfs_inode.c:62:\treturn write_stream_pool_count(\u0026xfs_inode_buftarg(ip)-\u003ebt_stream_pool);\nfs/xfs/xfs_inode.c-63-}\n--\nfs/xfs/xfs_inode.c=67=xfs_inode_set_write_stream(\n--\nfs/xfs/xfs_inode.c-82-\nfs/xfs/xfs_inode.c:83:\ttarget = xfs_inode_buftarg(ip);\nfs/xfs/xfs_inode.c-84-\tid = write_stream_get_id(fd_file(f), \u0026target-\u003ebt_stream_pool);\n--\nfs/xfs/xfs_inode.h=351=static inline bool xfs_inode_has_bigrtalloc(const struct xfs_inode ip)\n--\nfs/xfs/xfs_inode.h-358- /\nfs/xfs/xfs_inode.h:359:#define xfs_inode_buftarg(ip) \\\nfs/xfs/xfs_inode.h-360-\t(XFS_IS_REALTIME_INODE(ip) ? \\\n--\nfs/xfs/xfs_inode.h=363=static inline bool xfs_inode_can_hw_atomic_write(const struct xfs_inode ip)\n--\nfs/xfs/xfs_inode.h-367-\nfs/xfs/xfs_inode.h:368:\treturn xfs_inode_buftarg(ip)-\u003ebt_awu_max \u003e 0;\nfs/xfs/xfs_inode.h-369-}\n--\nfs/xfs/xfs_inode.h=614=static inline void xfs_update_stable_writes(struct xfs_inode ip)\nfs/xfs/xfs_inode.h-615-{\nfs/xfs/xfs_inode.h:616:\tif (bdev_stable_writes(xfs_inode_buftarg(ip)-\u003ebt_bdev))\nfs/xfs/xfs_inode.h-617-\t\tmapping_set_stable_writes(VFS_I(ip)-\u003ei_mapping);\n--\nfs/xfs/xfs_ioctl.c=1225=xfs_ioc_write_stream_alloc(\n--\nfs/xfs/xfs_ioctl.c-1236-\tmax = xfs_inode_max_write_streams(ip);\nfs/xfs/xfs_ioctl.c:1237:\ttarget = xfs_inode_buftarg(ip);\nfs/xfs/xfs_ioctl.c-1238-\txfs_iunlock(ip, XFS_ILOCK_SHARED);\n--\nfs/xfs/xfs_iomap.c=100=xfs_bmbt_to_iomap(\n--\nfs/xfs/xfs_iomap.c-108-\tstruct xfs_mount\tmp = ip-\u003ei_mount;\nfs/xfs/xfs_iomap.c:109:\tstruct xfs_buftarg\ttarget = xfs_inode_buftarg(ip);\nfs/xfs/xfs_iomap.c-110-\n--\nfs/xfs/xfs_iomap.c=174=xfs_hole_to_iomap(\n--\nfs/xfs/xfs_iomap.c-179-{\nfs/xfs/xfs_iomap.c:180:\tstruct xfs_buftarg\ttarget = xfs_inode_buftarg(ip);\nfs/xfs/xfs_iomap.c-181-\n--\nfs/xfs/xfs_iomap.c=817=xfs_bmap_hw_atomic_write_possible(\n--\nfs/xfs/xfs_iomap.c-844-\t /\nfs/xfs/xfs_iomap.c:845:\treturn len \u003c= xfs_inode_buftarg(ip)-\u003ebt_awu_max;\nfs/xfs/xfs_iomap.c-846-}\n--\nfs/xfs/xfs_iops.c=574=xfs_report_dioalign(\n--\nfs/xfs/xfs_iops.c-577-{\nfs/xfs/xfs_iops.c:578:\tstruct xfs_buftarg\ttarget = xfs_inode_buftarg(ip);\nfs/xfs/xfs_iops.c-579-\tstruct block_device\tbdev = target-\u003ebt_bdev;\n--\nfs/xfs/xfs_iops.c=651=xfs_get_atomic_write_max_opt(\n--\nfs/xfs/xfs_iops.c-665-\t /\nfs/xfs/xfs_iops.c:666:\treturn min(awu_max, xfs_inode_buftarg(ip)-\u003ebt_awu_max);\nfs/xfs/xfs_iops.c-667-}\n--\nfs/xfs/xfs_iops.c=1345=xfs_inode_supports_dax(\n--\nfs/xfs/xfs_iops.c-1358-\t/ Device has to support DAX too. /\nfs/xfs/xfs_iops.c:1359:\treturn xfs_inode_buftarg(ip)-\u003ebt_daxdev != NULL;\nfs/xfs/xfs_iops.c-1360-}\n--\nfs/xfs/xfs_log.c=287=xfs_log_writable(\n--\nfs/xfs/xfs_log.c-297-\t\treturn false;\nfs/xfs/xfs_log.c:298:\tif (xfs_readonly_buftarg(mp-\u003em_ddev_targp))\nfs/xfs/xfs_log.c-299-\t\treturn false;\nfs/xfs/xfs_log.c:300:\tif (xfs_readonly_buftarg(mp-\u003em_log-\u003el_targ))\nfs/xfs/xfs_log.c-301-\t\treturn false;\n--\nfs/xfs/xfs_log_recover.c=1236=xlog_find_tail(\n--\nfs/xfs/xfs_log_recover.c-1360-\t /\nfs/xfs/xfs_log_recover.c:1361:\tif (!xfs_readonly_buftarg(log-\u003el_targ))\nfs/xfs/xfs_log_recover.c-1362-\t\terror = xlog_clear_stale_blocks(log, tail_lsn);\n--\nfs/xfs/xfs_mount.c=688=xfs_calc_group_awu_max(\n--\nfs/xfs/xfs_mount.c-692-\tstruct xfs_groups\tg = \u0026mp-\u003em_groups[type];\nfs/xfs/xfs_mount.c:693:\tstruct xfs_buftarg\tbtp = xfs_group_type_buftarg(mp, type);\nfs/xfs/xfs_mount.c-694-\n--\nfs/xfs/xfs_mount.c=1534=xfs_dev_is_read_only(\n--\nfs/xfs/xfs_mount.c-1537-{\nfs/xfs/xfs_mount.c:1538:\tif (xfs_readonly_buftarg(mp-\u003em_ddev_targp) \|\|\nfs/xfs/xfs_mount.c:1539:\t xfs_readonly_buftarg(mp-\u003em_logdev_targp) \|\|\nfs/xfs/xfs_mount.c:1540:\t (mp-\u003em_rtdev_targp \u0026\u0026 xfs_readonly_buftarg(mp-\u003em_rtdev_targp))) {\nfs/xfs/xfs_mount.c-1541-\t\txfs_notice(mp, \"%s required on read-only device.\", message);\n--\nfs/xfs/xfs_mount.h=816=static inline struct xfs_buftarg \nfs/xfs/xfs_mount.h:817:xfs_group_type_buftarg(\nfs/xfs/xfs_mount.h-818-\tstruct xfs_mount\tmp,\n--\nfs/xfs/xfs_notify_failure.c=240=xfs_dax_notify_dev_failure(\n--\nfs/xfs/xfs_notify_failure.c-257-\nfs/xfs/xfs_notify_failure.c:258:\terror = xfs_dax_translate_range(xfs_group_type_buftarg(mp, type),\nfs/xfs/xfs_notify_failure.c-259-\t\t\toffset, len, \u0026daddr, \u0026bblen);\n--\nfs/xfs/xfs_super.c=467=xfs_open_devices(\n--\nfs/xfs/xfs_super.c-501-\t /\nfs/xfs/xfs_super.c:502:\tmp-\u003em_ddev_targp = xfs_alloc_buftarg(mp, sb-\u003es_bdev_file);\nfs/xfs/xfs_super.c-503-\tif (IS_ERR(mp-\u003em_ddev_targp)) {\n--\nfs/xfs/xfs_super.c-509-\tif (rtdev_file) {\nfs/xfs/xfs_super.c:510:\t\tmp-\u003em_rtdev_targp = xfs_alloc_buftarg(mp, rtdev_file);\nfs/xfs/xfs_super.c-511-\t\tif (IS_ERR(mp-\u003em_rtdev_targp)) {\n--\nfs/xfs/xfs_super.c-518-\tif (logdev_file \u0026\u0026 file_bdev(logdev_file) != ddev) {\nfs/xfs/xfs_super.c:519:\t\tmp-\u003em_logdev_targp = xfs_alloc_buftarg(mp, logdev_file);\nfs/xfs/xfs_super.c-520-\t\tif (IS_ERR(mp-\u003em_logdev_targp)) {\n--\nfs/xfs/xfs_super.c-535-\tif (mp-\u003em_rtdev_targp)\nfs/xfs/xfs_super.c:536:\t\txfs_free_buftarg(mp-\u003em_rtdev_targp);\nfs/xfs/xfs_super.c-537-\tmp-\u003em_rtdev_targp = NULL;\nfs/xfs/xfs_super.c:538:\trtdev_file = NULL;\t/ released by xfs_free_buftarg() */\nfs/xfs/xfs_super.c-539- out_free_ddev_targ:\nfs/xfs/xfs_super.c:540:\txfs_free_buftarg(mp-\u003em_ddev_targp);\nfs/xfs/xfs_super.c-541-\tmp-\u003em_ddev_targp = NULL;\n--\nfs/xfs/xfs_super.c=601=xfs_setup_devices(\n--\nfs/xfs/xfs_super.c-605-\nfs/xfs/xfs_super.c:606:\terror = xfs_configure_buftarg(mp-\u003em_ddev_targp, mp-\u003em_sb.sb_sectsize,\nfs/xfs/xfs_super.c-607-\t\t\tmp-\u003em_sb.sb_dblocks);\n--\nfs/xfs/xfs_super.c-620-\t\t\tlog_sector_size = mp-\u003em_sb.sb_logsectsize;\nfs/xfs/xfs_super.c:621:\t\terror = xfs_configure_buftarg(mp-\u003em_logdev_targp,\nfs/xfs/xfs_super.c-622-\t\t\t\tlog_sector_size, mp-\u003em_sb.sb_logblocks);\n--\nfs/xfs/xfs_super.c-634-\t} else if (mp-\u003em_rtname) {\nfs/xfs/xfs_super.c:635:\t\terror = xfs_configure_buftarg(mp-\u003em_rtdev_targp,\nfs/xfs/xfs_super.c-636-\t\t\t\tmp-\u003em_sb.sb_sectsize, mp-\u003em_sb.sb_rblocks);\n--\nfs/xfs/xfs_super.c=851=xfs_mount_free(\n--\nfs/xfs/xfs_super.c-854-\tif (mp-\u003em_logdev_targp \u0026\u0026 mp-\u003em_logdev_targp != mp-\u003em_ddev_targp)\nfs/xfs/xfs_super.c:855:\t\txfs_free_buftarg(mp-\u003em_logdev_targp);\nfs/xfs/xfs_super.c-856-\tif (mp-\u003em_rtdev_targp \u0026\u0026 mp-\u003em_rtdev_targp != mp-\u003em_ddev_targp)\nfs/xfs/xfs_super.c:857:\t\txfs_free_buftarg(mp-\u003em_rtdev_targp);\nfs/xfs/xfs_super.c-858-\tif (mp-\u003em_ddev_targp)\nfs/xfs/xfs_super.c:859:\t\txfs_free_buftarg(mp-\u003em_ddev_targp);\nfs/xfs/xfs_super.c-860-\n--\nfs/xfs/xfs_super.c=2050=xfs_remount_rw(\n--\nfs/xfs/xfs_super.c-2056-\tif (mp-\u003em_logdev_targp \u0026\u0026 mp-\u003em_logdev_targp != mp-\u003em_ddev_targp \u0026\u0026\nfs/xfs/xfs_super.c:2057:\t xfs_readonly_buftarg(mp-\u003em_logdev_targp)) {\nfs/xfs/xfs_super.c-2058-\t\txfs_warn(mp,\n--\nfs/xfs/xfs_super.c-2062-\nfs/xfs/xfs_super.c:2063:\tif (mp-\u003em_rtdev_targp \u0026\u0026 xfs_readonly_buftarg(mp-\u003em_rtdev_targp)) {\nfs/xfs/xfs_super.c-2064-\t\txfs_warn(mp,\n" }
63/3	2026/09/23 06:49	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 57795 output: 40 thoughts: 28 Thoughts: Here's a summary of my thought process, as requested: Diving into `xfs_alloc_buftarg` Okay, time to get my hands dirty. I'm going to take a closer look at `xfs_alloc_buftarg`. I know it's located in `fs/xfs/xfs_buf.c`, so I'll navigate to that file. My understanding is this function is crucial for buffer target allocation within XFS, and I need to refresh my memory on the specifics of how it works, how it's used, and what potential issues might arise in certain scenarios. Let's see what we can find.
64/3	2026/09/23 06:49	tool	read-file	0m Args: { "File": "fs/xfs/xfs_buf.c", "FirstLine": 1799, "LineCount": 40 } Results: { "Contents": "1799:\tstruct xfs_buftarg \n1800:\txfs_alloc_buftarg(\n1801:\t\tstruct xfs_mount\tmp,\n1802:\t\tstruct file\t\tbdev_file)\n1803:\t{\n1804:\t\tstruct xfs_buftarg\tbtp;\n1805:\t\tconst struct dax_holder_operations ops = NULL;\n1806:\t\tint\t\t\terror;\n1807:\t\n1808:\t\n1809:\t#if defined(CONFIG_FS_DAX) \u0026\u0026 defined(CONFIG_MEMORY_FAILURE)\n1810:\t\tops = \u0026xfs_dax_holder_operations;\n1811:\t#endif\n1812:\t\tbtp = kzalloc_obj(btp, GFP_KERNEL \| __GFP_NOFAIL);\n1813:\t\n1814:\t\tbtp-\u003ebt_mount = mp;\n1815:\t\tbtp-\u003ebt_file = bdev_file;\n1816:\t\tbtp-\u003ebt_bdev = file_bdev(bdev_file);\n1817:\t\tbtp-\u003ebt_dev = btp-\u003ebt_bdev-\u003ebd_dev;\n1818:\t\tbtp-\u003ebt_daxdev = fs_dax_get_by_bdev(btp-\u003ebt_bdev, \u0026btp-\u003ebt_dax_part_off,\n1819:\t\t\t\t\t\t mp, ops);\n1820:\t\n1821:\t\t/\n1822:\t\t Flush and invalidate all devices' pagecaches before reading any\n1823:\t\t * metadata because XFS doesn't use the bdev pagecache.\n1824:\t\t /\n1825:\t\terror = sync_blockdev(btp-\u003ebt_bdev);\n1826:\t\tif (error)\n1827:\t\t\tgoto error_free;\n1828:\t\n1829:\t\t/\n1830:\t\t * When allocating the buftargs we have not yet read the super block and\n1831:\t\t * thus don't know the file system sector size yet.\n1832:\t\t */\n1833:\t\tbtp-\u003ebt_meta_sectorsize = bdev_logical_block_size(btp-\u003ebt_bdev);\n1834:\t\tbtp-\u003ebt_meta_sectormask = btp-\u003ebt_meta_sectorsize - 1;\n1835:\t\n1836:\t\terror = xfs_init_buftarg(btp, btp-\u003ebt_meta_sectorsize,\n1837:\t\t\t\t\tmp-\u003em_super-\u003es_id);\n1838:\t\tif (error)\n" }
65/3	2026/09/23 06:49	llm	kmsan-evaluator	0m Model: gemini-3.8-flash Args: null Results: null Tokens: input: 58699 output: 481 thoughts: 1997 Thoughts: KMSAN Assessment: No Need for KMSAN in this Patch Okay, let me walk through this. I see that `btp` is `kzalloc_obj`-allocated, which means it's zero-initialized. The code then initializes streams via `xfs_buftarg_init_streams` or zeros the `bt_stream_pool` if not. I'm noting that `write_stream_pool_destroy` is safe because `bitmap_free(NULL)` is handled gracefully. Now looking at `xfs_inode_set_write_stream`, I see that it validates the file descriptor and handles some mutual exclusion conditions between write streams and filestreams, and also with write life time hint. I've checked all the touched files, and the important thing is to make sure we don't have user-space exposure or uninitialized reads. `FS_IOC_WRITE_STREAM_GET_MAX` uses a simple integer, `__u32`, which is initialized. No structs are sent. There are no `copy_to_user` calls that could leak information either. Next, I looked for uninitialized variables or struct fields read in conditional logic. `i_write_stream` is initialized to 0. The `iomap` struct's `write_stream` is populated correctly by reading the value of `i_write_stream`. The `write_stream` struct itself is `kzalloc_obj`-allocated and initialized. The `write_stream_pool` is also zeroed and initialized through the methods mentioned earlier. The `xfs_ioc_write_stream_set` handles copy from user with error returns if it fails. I've thought through potential memory errors. Any use-after-free scenarios with write streams, files, or inodes would be caught by KASAN. Locking issues with `spin_lock` and `xfs_ilock` are LOCKDEP-detectable. Division by zero in `xfs_bmap_write_stream_agno` would trigger the division by zero trap or UB sanitizer. Out-of-bounds bitmap access is, again, KASAN-catchable. Finally, let's see if this patch introduces any of the KMSAN-specific concerns. It doesn't modify or introduce: kernel structures sent to userspace with uninitialized fields, conditional logic relying on uninitialized variables, allocation of complex structures with uninitialized fields, or code that allows access to uninitialized bytes in buffers. Everything is either explicitly initialized or zeroed. So, according to the guidance, this patch is safe from KMSAN concerns. KASAN and standard bug detectors should be sufficient. I'm setting `NeedsKMSAN=false` and that's the final answer.
66/3	2026/09/23 06:49	tool	set-results	0m Args: { "KMSANReasoning": "The patch series introduces generic write stream fd management and integrates write stream awareness into VFS/fcntl, iomap (DIO and writeback), and XFS block allocation.\n\nAn analysis of potential uninitialized memory risks reveals:\n1. Data structures and fields:\n - `struct write_stream` is allocated via `kzalloc_obj` in `write_stream_alloc_fd()`, ensuring all fields are zeroed before assignment.\n - `struct write_stream_pool` bitmap allocations use `bitmap_zalloc`.\n - `inode-\u003ei_write_stream` is explicitly initialized to 0 in `inode_init_always_gfp()`.\n - The newly added field `write_stream` in `struct iomap` is populated in `xfs_bmbt_to_iomap()`, while other iomap consumers benefit from zero-initialization in `iomap_iter_continue()` (via `memset`) and designated initializers (`struct iomap_iter iter = ...`, `struct iomap_writepage_ctx wpc = ...`).\n2. User-space copies / info-leaks:\n - `FS_IOC_WRITE_STREAM_GET_MAX` uses `put_user(max, ...)` where `max` is a fully initialized `__u32` scalar value.\n - `FS_IOC_WRITE_STREAM_ALLOC` returns the file descriptor integer directly.\n - `FS_IOC_WRITE_STREAM_SET` only performs `copy_from_user` to read the input parameters.\n - No structures containing padding or uninitialized fields are copied to user space.\n3. Bug profiles:\n - Potential issues in this patch series pertain to reference counting (`mntget`/`mntput`), synchronization (`i_lock`, `pool-\u003elock`, `XFS_ILOCK`), or lifecycle management/UAF, all of which are properly detected by standard KASAN, LOCKDEP, and UBSAN.\n\nTherefore, there is no uninitialized memory usage or info-leak risk that would require a dedicated KMSAN fuzzing session.", "NeedsKMSAN": false } Results: { "KMSANReasoning": "The patch series introduces generic write stream fd management and integrates write stream awareness into VFS/fcntl, iomap (DIO and writeback), and XFS block allocation.\n\nAn analysis of potential uninitialized memory risks reveals:\n1. Data structures and fields:\n - `struct write_stream` is allocated via `kzalloc_obj` in `write_stream_alloc_fd()`, ensuring all fields are zeroed before assignment.\n - `struct write_stream_pool` bitmap allocations use `bitmap_zalloc`.\n - `inode-\u003ei_write_stream` is explicitly initialized to 0 in `inode_init_always_gfp()`.\n - The newly added field `write_stream` in `struct iomap` is populated in `xfs_bmbt_to_iomap()`, while other iomap consumers benefit from zero-initialization in `iomap_iter_continue()` (via `memset`) and designated initializers (`struct iomap_iter iter = ...`, `struct iomap_writepage_ctx wpc = ...`).\n2. User-space copies / info-leaks:\n - `FS_IOC_WRITE_STREAM_GET_MAX` uses `put_user(max, ...)` where `max` is a fully initialized `__u32` scalar value.\n - `FS_IOC_WRITE_STREAM_ALLOC` returns the file descriptor integer directly.\n - `FS_IOC_WRITE_STREAM_SET` only performs `copy_from_user` to read the input parameters.\n - No structures containing padding or uninitialized fields are copied to user space.\n3. Bug profiles:\n - Potential issues in this patch series pertain to reference counting (`mntget`/`mntput`), synchronization (`i_lock`, `pool-\u003elock`, `XFS_ILOCK`), or lifecycle management/UAF, all of which are properly detected by standard KASAN, LOCKDEP, and UBSAN.\n\nTherefore, there is no uninitialized memory usage or info-leak risk that would require a dedicated KMSAN fuzzing session.", "NeedsKMSAN": false }

LLM Calls Summary:
Total Calls	Total Tokens	Avg Tokens	Total Duration (Seconds)	Avg Duration (Seconds)

Tool Calls Summary:
Total Calls	Total Duration (Seconds)	Avg Duration (Seconds)